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IBM Z

IBM Z is a family of enterprise-grade mainframe computers developed by , representing the latest evolution in the company's long-standing line of systems designed for mission-critical workloads, offering unparalleled security, reliability, and scalability to handle massive transaction volumes in cloud environments. Introduced in 2000 with the zSeries 900 to meet the demands of e-business and internet-scale computing, IBM Z builds on over 50 years of mainframe innovation tracing back to the System/360 in the , emphasizing "zero downtime" reliability through advanced fault-tolerant and backward compatibility with legacy systems. Key milestones include the 2003 zSeries 990, capable of processing 9 billion ; the 2015 z13, which introduced pervasive real-time ; the 2022 z16 with integrated acceleration for fraud detection; and the 2025 z17, announced in April and powered by the Telum II processor to enhance integration, security, and resiliency in multicloud setups. At its core, IBM Z leverages the and S/390 chip family, featuring large caches, multiple specialty processors for tasks like and , and support for operating systems such as , , z/VSE, z/TPF, and distributions including , , and . These systems process up to 1 trillion secure transactions daily, execute billions of real-time calculations, and incorporate quantum-safe , self-checking , and -driven detection to achieve near-100% uptime and protect against cyber threats. IBM Z powers for industries worldwide, serving 45 of the top 50 banks, 67 of the Fortune 100 companies, and leading organizations in , healthcare, , , and airlines, where it consolidates workloads from thousands of distributed servers into a single, energy-efficient platform that reduces operational costs and environmental impact.

Overview

Definition and Purpose

IBM Z is a family of high-end mainframe computers developed by , utilizing the instruction set to support mission-critical enterprise computing. These systems are engineered for processing vast amounts of data in , including , data analytics, and secure computing environments where reliability and performance are paramount. The primary purposes of IBM Z include managing enormous transaction volumes, such as the billions processed daily in . It also facilitates integration into hybrid environments, enabling seamless data flow between on-premises mainframes and applications while maintaining and low . Additionally, IBM Z is designed to deliver exceptional , targeting 99.999% uptime to minimize disruptions in critical operations. In July 2017, IBM rebranded its mainframe lineup from System z—introduced in 2000—to , underscoring its evolution toward enhanced integration with and technologies. This family serves core markets such as banking, , healthcare, and , where it powers essential workloads like online transactions, , patient data management, and operations. The current z17 model, announced in 2025, further advances these capabilities with enhanced AI integration and resiliency.

Key Characteristics

IBM Z systems are engineered for exceptional scalability, enabling the support of thousands of virtual machines per system through technology operating within logical partitions (LPARs). This capability allows enterprises to consolidate thousands of workloads efficiently on a single mainframe, optimizing resource utilization for diverse applications ranging from traditional to modern cloud-native environments. Logical partitioning via PR/SM provides up to 85 concurrent LPARs, further enhancing flexibility in workload isolation and management. Reliability is a of IBM Z design, incorporating built-in redundancy across hardware components, advanced error correction mechanisms, and fault-tolerant architectures that achieve (MTBF) measured in decades. These (RAS) features deliver over 99.999% availability, minimizing downtime for mission-critical operations and ensuring continuous business continuity. Security is embedded at the hardware level with pervasive capabilities that protect , at rest, and in use without performance degradation, supported by tamper-resistant cryptographic such as Crypto Express adapters. This design safeguards sensitive information against sophisticated threats, making IBM Z a preferred platform for regulated industries handling high-volume financial and . In terms of performance, IBM Z can process up to 12.6 billion transactions per day while supporting low-latency , enabling rapid decision-making in high-throughput environments. Additionally, models like the z16 with the Telum processor and the z17 with Telum II integrate on-chip accelerators to enhance inferencing for enterprise AI workloads. A defining trait of IBM Z is its , allowing unmodified execution of applications originally developed for the System/360 architecture from the 1960s, ensuring long-term investment protection across generations of hardware.

History

Origins in System/360

IBM announced the System/360 family of computers on April 7, 1964, marking the introduction of the first compatible line of computers designed to serve a wide range of applications from to scientific . This ambitious project, which cost approximately $5 billion in development (equivalent to over $30 billion in today's dollars), represented 's largest commercial investment to date and aimed to replace the company's fragmented lineup of incompatible machines with a unified architecture. The System/360 shifted the computing paradigm by adopting a binary architecture that emphasized compatibility across models, allowing customers to scale their systems without rewriting software. Key innovations in the System/360 included a standardized instruction set that ensured upward and downward , enabling programs to run seamlessly on different models within the family. It also introduced capabilities, which allowed for efficient and by treating more memory as available than physically present, thus supporting larger workloads without hardware redesigns. Additionally, the channel-based I/O system optimized data transfer between the CPU and peripherals, using dedicated channels to handle up to 54 devices efficiently and reducing CPU overhead for operations. These features collectively enabled and a that revolutionized how enterprises approached . The impact of the System/360 was profound, transforming the industry from a landscape of siloed, incompatible systems to a cohesive ecosystem that fostered the growth of third-party software and peripherals. IBM's annual revenue more than doubled from $3.2 billion in 1964 to $7.5 billion by 1970, driven by the success of System/360. The family captured approximately 70% of the global computer by the early 1970s, dominating enterprise computing and setting standards that influenced subsequent architectures. Among the early models, the System/360 Model 91 was tailored for scientific computing, featuring high-speed processing optimized for applications like and theoretical simulations, with two units delivered to NASA's in 1967 and 1968. At the high end, the Model 195, announced in 1969, provided twice the performance of the Model 85 and supported demanding workloads with up to 4 of and advanced capabilities. These models exemplified the family's versatility, paving the way for the evolutionary lineage leading to modern in IBM Z systems.

Evolution through zSeries to Modern IBM Z

In 1990, IBM introduced the System/390 (S/390) family, succeeding the System/370, and incorporated the Enterprise Systems Architecture/390 (ESA/390), which enhanced capabilities through improved interpretive-execution support for virtual machines. This architecture laid the groundwork for more efficient resource sharing and workload isolation in enterprise environments. The transition to the zSeries branding occurred in 2000 with the launch of the zSeries 900 (z900), marking the introduction of the 64-bit and native support for workloads on mainframes. This shift enabled larger address spaces, better scalability for e-business applications, and broader interoperability with open-source ecosystems. In 2006, rebranded the zSeries to System z, aligning the nomenclature with its eServer branding strategy while emphasizing enterprise-class reliability and zero-downtime operations. This period saw continued evolution, including the 2003 release of the zSeries 990 (z990), which pioneered a book-based packaging design allowing up to four books for modular scalability and up to 48 processor units. A significant milestone came in 2010 with the zEnterprise 196 (z196), the first System z to implement , enabling superscalar processing at 5.2 GHz to dynamically reorder instructions and reduce latency for compute-intensive tasks. Concurrently, the integration of specialty engines advanced, with the z Application Assist (zAAP) offloading and XML processing from central processors, and the CP Assist for Cryptographic Function (CPACF) providing for cryptographic operations like and algorithms. The branding evolved further in 2017 to with the z14 announcement, positioning the platform for the cloud era by emphasizing pervasive and hybrid integration capabilities. Entering the 2020s, the focus shifted toward hybrid cloud environments, exemplified by the 2022 , which integrated on-chip for real-time inferencing and quantum-safe to support secure, scalable cloud-native workloads. In 2025, the advanced this trajectory with the Telum II processor and Spyre , embedding generative hardware directly into the mainframe for on-premises threat detection and decision-making at scale.

Architecture

z/Architecture Fundamentals

is a 64-bit complex instruction set computing (CISC) (ISA) developed by , introduced in October 2000 with the z900 server as a successor to the Enterprise Systems Architecture/390 (ESA/390). It extends ESA/390 by introducing full 64-bit addressing, known as millennium addressing, to support vast memory spaces beyond 2 gigabytes and enable efficient handling of large-scale , while incorporating capabilities for improved . This architecture powers all IBM Z mainframes, providing a robust foundation for enterprise workloads requiring high reliability and performance. The ISA encompasses over 1,000 instructions, categorized into general-purpose, floating-point, , and control operations, designed to optimize and data analytics. Notable among these are the facilities, introduced with the z13 in 2015, which support (SIMD) operations on 128-bit vectors to accelerate and tasks, such as data compression and cryptographic functions. Additionally, decimal floating-point instructions, compliant with IEEE 754-2008 standards, facilitate precise financial calculations by avoiding rounding errors common in binary , making them essential for banking and transaction-heavy applications. z/Architecture maintains through multiple addressing modes: 24-bit for legacy System/370 applications, 31-bit for ESA/390-era software, and 64-bit for modern 64-bit virtual and real addresses up to 16 exabytes. Programs can dynamically switch between these modes via the (PSW), ensuring seamless execution of mixed legacy and contemporary code without recompilation. For , includes specialized instructions such as MOVE WITH DESTINATION KEY CHECK and COMPARE AND FORM CODEWORD, which compute checksums and perform detection on data blocks, aiding in recovery from transmission or storage . These mechanisms, combined with hardware-level correction, support resilient operation in mission-critical environments. The has evolved through multiple editions of its defining specification, with the fifteenth edition (SA22-7832-14) released in June 2025 introducing enhancements for the z17 , including new instructions such as BDEPG, BEXTG, and CAL to improve performance, integration, and security. These updates build on prior extensions, such as the -specific enhancements in the fourteenth edition (May 2022) with instructions for and quantization to accelerate processing directly in hardware, and features that enable efficient logical partitioning, as detailed in subsequent architectural components.

Virtualization and Partitioning

Logical partitioning (LPAR) on IBM Z systems is facilitated by the Processor Resource/System Manager (PR/SM) , which divides the physical machine into multiple isolated partitions, each capable of running an independent operating system as if it were a standalone server. Introduced with the series processors in 1988, PR/SM provides type-1 , enabling secure resource sharing while maintaining strict isolation between partitions to prevent interference or data leakage. This facility has evolved significantly, with early implementations supporting limited partitions and later enhancements, such as those in the z990 model introduced in , expanding capacity to up to 30 LPARs per system. Building on LPAR, the offers at the operating system level, allowing multiple guest operating systems—such as , , or z/TPF—to run concurrently within a single LPAR as virtual machines. leverages instructions for efficient , supporting hundreds to thousands of guest virtual machines per LPAR, depending on resource availability and configuration. In modern IBM Z systems like the z17, this enables up to 85 LPARs overall, with dynamic scaling to accommodate dense virtualization environments. IBM Z supports dynamic through concurrent reconfiguration features, permitting the live addition or removal of central processing units (CPUs) and without system downtime or partition IPL. For instance, processors can be reassigned between LPARs or upgraded via Capacity on Demand mechanisms, while —up to 64 TB system-wide on the z17—can be dynamically reallocated using features like Dynamic Memory Relocation to optimize and utilization. These capabilities, integrated with PR/SM, allow seamless workload balancing across s. Security in IBM Z virtualization is enforced at the hardware level by PR/SM, which provides robust isolation between LPARs to prevent cross-partition attacks, earning EAL5+ certification for its partitioning mechanisms. This hardware-enforced separation ensures that resources allocated to one partition remain inaccessible to others, even in the presence of software vulnerabilities, supporting secure multi-tenancy in consolidated environments. further extends this isolation to guest virtual machines, maintaining integrity through architectural controls without compromising performance.

Models

IBM z17

The IBM z17 mainframe, announced on April 8, 2025, as the successor to the z16, represents a significant advancement in enterprise computing with a focus on integrated capabilities. Powered by the Telum II processor, which features eight high-performance cores operating at 5.5 GHz and contains 43 billion transistors fabricated on Samsung's , the z17 is designed to handle mission-critical workloads at scale. This processor includes a 40% larger cache at 36 MB per chip and a 360 MB virtual L3 cache, enabling enhanced performance for transactional applications. In terms of capacity, the z17 supports up to 208 configurable processor units across configurations such as Max43, Max90, Max136, and Max183, paired with a maximum of 64 TB of system memory to accommodate large-scale in-memory databases and AI models. It can process up to 35 billion transactions per day while performing 450 billion AI inference operations daily at latencies as low as 1 ms, as demonstrated in fraud detection benchmarks using models like those for credit card transactions. Key innovations include an on-chip AI accelerator integrated into the Telum II, which delivers 50% more inference performance than the z16's Telum I and supports real-time AI without data movement; an embedded Data Processing Unit (DPU) for offloading networking and I/O tasks to improve throughput; and enhanced quantum-safe cryptography via Crypto Express 8S adapters, incorporating post-quantum algorithms to protect against future quantum threats. The z17 achieves power efficiency improvements of 17-27% over the z16 through architectural optimizations like fine-grained voltage control and advanced thermal management, including an internal liquid-cooling system using and water mixtures for chip-level heat dissipation. Entry-level models start at approximately $250,000, with general availability beginning June 18, 2025. These enhancements position the z17 as a platform optimized for hybrid cloud environments, emphasizing , , and AI-driven decision-making in industries like and healthcare.

IBM z16

The IBM z16 mainframe was announced on April 5, 2022, as the industry's first system to integrate an on-chip for real-time inferencing directly within its , enabling at scale with embedded capabilities. It features the Telum processor, fabricated on a with eight cores per chip operating at 5.2 GHz and a dual-chip module containing 22 billion transistors. The design emphasizes AI-driven workloads, with each core accessing a dedicated delivering over six teraflops of compute capacity per chip for low-latency inferencing. The z16 supports configurations of up to 200 active and 40 terabytes of addressable across four central complex () drawers, providing 25% more capacity per drawer compared to its predecessor. Performance improvements include up to 40% better overall throughput than the , driven by 11% gains in single-thread performance, 1.5 times more cache per core (32 MB L2 per core), and reduced latency in the . Key innovations encompass support for PCIe Generation 5, which doubles bandwidth for storage and networking attachments to accelerate data access, alongside integrated cryptographic hardware for enhanced I/O security. On security, the z16 advances pervasive —introduced in prior generations—to cover all in flight and at rest, while introducing the first quantum-safe features via the Crypto Express 8s adapter, protecting against future threats without application changes. For deployment, it supports 2.5 and integrates with IBM Cloud Paks to facilitate hybrid cloud environments, allowing seamless extension of mainframe workloads to containerized applications across on-premises and public clouds.

IBM z15

The , announced on September 12, 2019, represents a significant advancement in enterprise , introducing enhanced capabilities for hybrid multicloud environments. Built on the z15 , it operates at a core frequency of 5.2 GHz and features a 12-core design fabricated using nm silicon-on-insulator technology, with each unit containing 9.2 billion transistors. The system is available in models ranging from Max34 to Max190, supporting configurations with one to five central processing complex () drawers for scalable deployment. Key capacity specifications include up to 190 central processors and 40 TB of redundant array of independent (RAIM), an increase from the 32 TB maximum of its predecessor, the z14. A notable innovation is the integrated accelerator for zEnterprise Data (zEDC), embedded in every , which accelerates compression and decompression tasks, reducing CPU cycles and I/O overhead for data-intensive operations by up to several times compared to software-only methods. The z15 also provides the first native support for all-flash storage systems, such as the DS8900F, enabling higher I/O throughput for mission-critical applications. Additionally, it supports 1 TB increments, facilitating large-scale in-memory analytics by allowing vast datasets to reside entirely in RAM without spilling to disk. In terms of efficiency, the z15 delivers up to a 25% increase in total system capacity for z/OS workloads over the z14, driven by architectural improvements in processor performance and I/O scalability. Its modular frame design, with up to four CPC frames and dedicated I/O drawers, simplifies nondisruptive upgrades by allowing incremental additions of processors, memory, and connectivity without requiring a full system replacement. The platform is particularly optimized for analytics, supporting accelerated processing for IBM Db2 queries and Apache Spark workloads through its high memory capacity and integrated compression, enabling faster insights from terabyte-scale datasets in hybrid cloud setups.

IBM z14

The IBM z14, announced on July 17, 2017, marked the debut of IBM's rebranded mainframe lineup as , emphasizing enhanced security and performance for enterprise workloads. This model utilizes the z14 processor, which operates at a clock speed of 5.2 GHz and supports up to 170 configurable central processing units (CPUs) in its maximum configuration across four central processing complex () drawers. The system supports up to 32 TB of total client memory, with a maximum of 16 TB allocatable per logical (LPAR), enabling scalable handling of large-scale and tasks. A key innovation in the z14 is its introduction of standard pervasive encryption, the first such implementation in mainframes, designed to protect and in transit without requiring application changes. This feature is powered by an inline encryption co-processor integrated into the central assist for cryptographic function (CPACF), which delivers up to six times the encryption performance of the prior z13 generation and reduces CPU overhead for secure data processing by approximately 90%. The co-processor accelerates symmetric key operations like encryption, minimizing latency and resource consumption for high-volume transactions. In terms of form factor, the z14 is available in single-frame configurations for entry-level models (such as M01 with one CPC drawer) or multi-frame setups for larger scales (up to M05 with four drawers), incorporating air- or water-cooled options for flexibility in data center environments. It also achieves improved I/O density through support for up to five PCIe Gen3 I/O drawers, each providing 32 slots and up to 160 GBps bidirectional bandwidth per drawer via features like zHyperLink Express. Performance-wise, the z14 delivers up to 35% greater total system capacity compared to the z13 Model NE1, driven by architectural enhancements including doubled on-chip per core and optimized , which contribute to higher throughput in applications. These improvements position the z14 as a robust for mission-critical workloads requiring reliability and efficiency.

IBM z13

The IBM z13, announced on January 14, 2015, represented a significant advancement in mainframe technology, introducing enhanced performance and integration capabilities for data-intensive workloads. Built on a new fabricated using a 22-nanometer process, the z13 featured an 8-core central (CP) chip operating at 5.0 GHz with approximately 4 billion transistors, enabling up to 141 configurable characterizable cores in its maximum configuration. This architecture supported up to 10 TB of real-addressable and incrementally matched (RAIM), a threefold increase over the previous zEnterprise EC12 generation, allowing for larger-scale and workload consolidation. The system delivered up to 40% more total capacity compared to the zEC12, with models ranging from the entry-level N30 to the high-end NE1, all supporting air- or water-cooled options for flexible deployment. A key innovation in the z13 was the introduction of simultaneous multithreading (SMT) with two threads per core for integrated facility for Linux (IFL) and zIIP specialty engines, providing up to a 1.2x capacity improvement for eligible workloads by better utilizing core resources such as caches and execution units. This feature, implemented transparently to applications and requiring version 2.1 or later, enhanced throughput for parallelizable tasks without altering software. More notably, the z13 was the first mainframe to integrate an accelerator via a (SIMD) facility, including 139 new vector instructions and 32 vector registers, enabling transaction analytics such as detection across 100% of transactions. This on-chip acceleration supported rapid processing of complex mathematical models, integrating with tools like IBM zAware for in system logs. The z13's design emphasized efficiency and I/O advancements, incorporating dedicated compression accelerators per core via the zEnterprise Data Compression (zEDC) feature for high-speed handling, alongside FICON Express16S channels operating at 16 Gbps to support video in workflows. In terms of power management, the system achieved 45% more compute capacity per watt than the zEnterprise EC12 through optimizations like dynamic frequency and voltage scaling, (HVDC) power delivery, and optional , which reduced overall for equivalent workloads. These improvements, combined with enhanced cryptographic performance via the Crypto Express5S adapter—offering up to 2x the throughput of prior generations—positioned the z13 as a resilient platform for secure, high-volume in environments.

zEnterprise Systems

The IBM zEnterprise systems, launched in 2010, represented a pivotal advancement in mainframe technology by introducing hybrid computing capabilities that unified mainframe reliability with distributed environments. The inaugural model, the zEnterprise 196, incorporated the z196 , which operated at a clock speed of 5.2 GHz and featured with a superscalar capable of processing up to five instructions per cycle. This utilized quad-core chips within multi-chip modules, supporting configurations of up to 80 units (PUs) configurable as central processors (CPs), integrated facility for Linux (IFLs), or specialty engines, alongside up to 3 TB of usable client memory across models such as M15, M32, M49, M66, and M80. Subsequent models expanded capacity and performance. The zEnterprise EC12 (zEC12), announced in 2012, employed an enhanced zEC12 processor at 5.5 GHz, delivering up to characterized and maintaining support for 3 TB of , with configurations across five models (, H43, H66, H89, HA1) that scaled from 20 to CPs. In 2013, the entry-level zEnterprise BC12 (zBC12) followed, offering a more affordable option with up to 10 CPs at a base frequency of 4.2 GHz and maximum of 256 GB, targeted at smaller-scale deployments while retaining compatibility with zEnterprise infrastructure. These systems supported up to 116 total in the zEC12 when including spares, emphasizing scalability for enterprise workloads. A core innovation of the zEnterprise family was the Unified Resource Manager, a firmware-based tool that provided centralized, policy-driven oversight of resources across mainframe and attached distributed components, enabling automated workload optimization, energy monitoring, and virtual lifecycle management for ensembles of up to eight nodes. This facilitated hybrid integration with the zEnterprise BladeCenter Extension (zBX), which accommodated x86 blades running alongside specialized accelerators, extending mainframe qualities of service like and resiliency to heterogeneous environments through private intra-ensemble networks. Additionally, the systems introduced copper-based interconnects via HCA2-C fanouts, operating at 6 Gb/s for faster internal data transfer between I/O components compared to prior fiber optics. As the final generation before the z13's emphasis on higher frequencies and pervasive encryption, zEnterprise systems served a transitional role from 2010 to 2014, bridging traditional System z virtualization with emerging hybrid cloud architectures while prioritizing energy-efficient designs like hybrid air and water cooling.

System z10 and Earlier Generations

The IBM System z10, announced on February 26, 2008, represented a significant advancement in mainframe technology with its z10 processor, fabricated on a 65 nm process node—the first sub-100 nm design in the System z lineage—operating at up to 4.4 GHz in a quad-core configuration. This processor enabled configurations of up to 64 cores per system, delivering up to 50% better performance for general workloads compared to prior generations while supporting enhanced virtualization through expanded logical partitions. A key innovation was the introduction of hardware-accelerated XML processing via dedicated instructions in the z/Architecture, which improved efficiency for data-intensive e-business applications by reducing software overhead in parsing and transforming XML data. The System z10 also emphasized energy efficiency, with features like dynamic power management that lowered operational costs for large-scale deployments. Preceding the z10, the System z9, announced in July 2005 and available from September 2005, utilized the z9 processor to support up to 54 central processing engines in its Enterprise Class model, marking an increase in scalability for workloads. It introduced LPAR as part of its Capacity on Demand offerings, allowing customers to temporarily activate additional logical partitions without intervention, thereby enhancing flexibility for fluctuating demands in virtualized environments. The z9 maintained with earlier systems while incorporating improved reliability features, such as enhanced error correction in memory subsystems, to support mission-critical operations. The zSeries era, spanning 2000 to 2004, laid the groundwork for modern IBM Z with the z900 (announced October 3, 2000) debuting full 64-bit addressing in , enabling vastly expanded memory capacities beyond the 2 GB limit of 31-bit systems and facilitating the integration of distributions for e-business applications. This shift supported running hundreds of virtual servers on a single mainframe, promoting consolidation and cost reductions, particularly for midrange configurations. The z990, announced in May 2003, advanced this with a modular book design—each book containing multiple processor units and shared cache—allowing scalable configurations from 1 to 4 books for up to 32 processors, which improved throughput for in e-business and database workloads. Across these generations, key trends included the 2000 transition to for handling larger datasets, progressive enhancements in via PR/SM logical partitioning to enable resource sharing among operating systems like and , and targeted cost reductions through on-demand capacity features that optimized midrange deployments without over-provisioning. All models from this period maintain full with contemporary IBM Z systems, ensuring that legacy applications and data from System z10 and earlier can execute seamlessly on platforms like the z17.

Hardware Features

Processors and Cache Hierarchy

The processors in IBM Z systems are designed for high-performance, reliable transaction processing, featuring multi-core chip architectures that integrate central processing units (CPUs) with specialized accelerators. Modern IBM Z processors, such as the Telum II chip used in the z17 model, incorporate eight high-frequency cores per chip, enabling scalable configurations up to 208 active cores across multiple chips in a central processing complex (CPC). Each core includes a dedicated L1 cache (128 KB for instructions and 128 KB for data) and a semi-private L2 cache of 36 MB per core, while the chip shares a virtual L3 cache of up to 360 MB for improved data access latency and bandwidth. This cache hierarchy optimizes for large-scale workloads by reducing cache misses and enhancing throughput, with the virtual L3 acting as an on-chip extension to support simultaneous multithreading (SMT) and out-of-order execution. The , introduced with the z990 in , enhances by grouping multiple into modular "books" that can be added incrementally to support growing workloads without full replacement. Each book typically contains 4 to 6 processor units, along with associated interconnects, allowing configurations from one to four books per for a total of up to 54 processors in early implementations, evolving to support denser chip packaging in later models. This facilitates balanced scaling of compute resources, I/O connectivity, and memory, ensuring consistent performance as capacity expands. IBM Z incorporates specialty engines as dedicated co-processors to offload specific tasks, improving efficiency and reducing costs for general-purpose CPUs. The Integrated Facility for Linux (IFL) provides processing capacity optimized for Linux and OpenSolaris workloads, while the z/OS Integrated Information Processor (zIIP) handles eligible database and IP workloads to minimize mainframe licensing expenses. The z/OS Application Assist Processor (zAAP), now largely integrated into zIIP functionality, accelerates Java and XML processing, and the Internal Coupling Facility (ICF) supports high-speed data sharing across systems. Additional accelerators include the Central Processor Assist for Cryptographic Functions (CPACF) for hardware-accelerated encryption and the IBM Z Integrated Accelerator for AI in Telum processors for machine learning inference, with support for workloads like SAP HANA through zIIP offloading. These engines operate at full capacity relative to central processors and are configurable via logical partitioning. Computing power in IBM Z is measured and licensed using Million Service Units (MSUs), defined as millions of service units per hour, serving as a standardized metric for capacity rather than direct millions of (MIPS), though 1 MSU approximates 8-10 MIPS depending on the model. MSU ratings determine full-capacity licensing for software, with subcapacity options allowing charges based on peak four-hour rolling average usage across logical partitions, enabling cost savings for variable workloads without over-provisioning. This model supports flexible deployment, including capacity upgrades. The evolution of IBM Z processors has progressed from in-order execution in the z9 generation, which processed instructions sequentially for reliability in environments, to introduced in the z196 processor for better and up to 50% performance gains over predecessors. Subsequent generations, including zEC12 and z13, refined this with larger out-of-order windows and (SMT) starting in z13, allowing two threads per core to improve utilization for diverse workloads like and transactions. These advancements, built on , prioritize resilience and scalability while integrating accelerators for emerging needs.

Memory and I/O Capabilities

IBM Z systems feature advanced memory subsystems designed for high reliability and scalability. In the IBM z17, the maximum total addressable reaches up to 64 TB per system, with up to 16 TB per central processor complex (CPC) drawer, utilizing DDR5 DIMMs protected by error-correcting code () and an 8-channel Reed-Solomon redundant array of independent (RAIM) design to detect and correct errors, including full chip and bus failures. This implementation, combined with symbol in the L2, L3, and L4 caches, ensures across the . Dynamic reconfiguration capabilities, such as LPAR dynamic storage reconfiguration and concurrent upgrades, allow nondisruptive addition or removal of without system outages, optimizing resource allocation via PR/SM functions like dynamic relocation. Input/output (I/O) architectures in IBM Z emphasize high-speed connectivity for enterprise workloads. FICON (Fibre Connection) channels provide fiber-optic interfaces for storage attachment, with the IBM z17 supporting up to 384 ports and earlier models like the z16 up to 512 channels (via 256 features with dual ports each), enabling distances up to 100 km in extended configurations. These channels support solid-state drives (SSDs) through over (FCP) mode, compatible with , , and KVM hypervisors, as well as tape libraries like the TS3310 via native FICON (CHPID type FC) using FC-SB-3/4 protocols for reliable data access. Starting with the z16, PCIe Generation 5 (Gen5) enhances internal expansion, integrating with features like zHyperLink Express for low-latency coupling, using x16 lanes bifurcated to x8 for improved bandwidth in I/O drawers. Coupling facilities are specialized components that facilitate Parallel Sysplex clustering, allowing up to 32 z/OS systems to operate as a unified platform by providing locking, caching, and list services for shared data. These facilities connect via dedicated coupling links and run Coupling Facility Control Code (CFCC) in dedicated logical partitions, ensuring data consistency and availability across systems without corruption, supporting applications like DB2 locks, IMS queues, and global resource serialization. From 2010 to 2015, the zEnterprise BladeCenter Extension (zBX) enabled hybrid integration by attaching x86 blades, such as HX5 running , to IBM Z ensembles via Intraensemble Data Network (IEDN) using 10 GbE OSA-Express links. This allowed non-mainframe workloads to leverage mainframe management and qualities of service, supporting up to 112 blades per zBX for consolidated . Recent IBM Z models achieve up to 16 TB/s of internal I/O throughput, driven by advancements in channel subsystems and accelerators like Integrated Coupling Accelerator (ICA SR) at 8 GBps per link, facilitating massive data processing in hybrid environments.

Cooling and Power Efficiency

IBM Z systems have evolved significantly in thermal management and optimization to support in dense environments. Early generations, such as the , relied primarily on to dissipate heat from processors and components. Starting with the IBM z13 introduced in , IBM implemented a closed internal loop specifically for the single chip modules (SCMs) in central processor complex () drawers, marking a shift toward more efficient liquid-based thermal management while retaining for other elements like specialty co-processor SCMs in air-cooled configurations. This internal liquid cooling approach in the z13 and subsequent models, including the z14, z15, z16, and z17, uses a radiator-based system where circulates through cold plates on modules before is transferred to air via redundant cooling units (RCUs). The design eliminates the need for external chilled connections, as seen in prior external liquid options, and incorporates redundant pumps and blowers for reliability. In -cooled z14 configurations, the full system benefits from enhanced dissipation, allowing higher clock speeds—up to 5.2 GHz—without increasing overall power draw compared to air-cooled variants. By z16 and z17, the cooling employs a pre-filled mixture of 40% and 60% in a closed loop, with thermal sensors controlling fan speeds to optimize and minimize use; drip pans and leak sensors further ensure safe operation without scheduled maintenance. Power management in IBM Z incorporates advanced techniques like dynamic voltage and frequency scaling through features such as Voltage Control (VCL), which adjusts processor voltage in based on demands to maintain while reducing consumption. The Telum II processor in the z17 enhances this with an on-chip voltage control loop, enabling finer-grained dynamic voltage management that reduces guard bands and improves without elevating peak power. Over 15 generations, IBM Z has achieved more than 125 times the per kilowatt, driven by process shrinks (e.g., 7 nm in z16 to 5 nm in z17), larger on-chip caches, and integrated accelerators that offload tasks with minimal overhead. The modular frame design facilitates seamless integration, with systems configurable across 1 to 4 standard 19-inch (42U) frames that can be bolted together and support both raised and non-raised floors. Each frame houses CPC drawers, I/O components, and RCUs, allowing scalable deployments up to 30 kW total power in multi-frame setups while enabling concurrent upgrades without . This evolution from air-cooled z9-era systems to fully internal liquid-cooled architectures in z14 and beyond supports denser configurations—up to 208 characterizable processors in z17—while prioritizing through reduced cooling infrastructure needs and proactive power capping.

Software Ecosystem

Operating Systems

IBM z/OS serves as the flagship operating system for IBM Z mainframes, designed to support high-volume batch processing and online transaction workloads in secure, continuously available environments. Introduced in 2000 as the successor to OS/390, z/OS has evolved to provide robust scalability, resource management, and integration capabilities for enterprise applications. The latest release, z/OS 3.2, became generally available on September 30, 2025, following its announcement on July 22, 2025, and introduces AI-enhanced management features such as the AI Framework for IBM z/OS to automate system operations and optimize performance. z/OS powers critical workloads, handling an estimated 70% of global financial transactions by value through its high-performance transaction processing support. IBM z/VM functions as a operating system and , enabling the hosting of multiple guest operating systems on a single IBM Z server to consolidate resources and improve efficiency. It supports a wide range of guests, including distributions, , z/VSE, and z/TPF, allowing organizations to run hundreds to thousands of virtual machines for diverse workloads such as and development testing. z/VM operates within logical partitions (LPARs) and provides security-rich partitioning through virtual machines, facilitating scalable resource allocation without dedicated hardware for each guest. IBM z/VSE is a compact operating system tailored for batch and transaction processing in smaller-scale mainframe environments, offering a simpler alternative to for cost-sensitive operations. It includes support for through the and integrates with DB2 for database management, enabling modern application development alongside legacy transaction systems like Transaction Server. IBM z/TPF is a specialized optimized for high-volume, mission-critical , particularly in industries requiring sub-second response times. It excels in applications such as , where it processes millions of transactions per day with near-real-time performance and . All primary IBM Z operating systems—z/OS, z/VM, z/VSE, and z/TPF—are fully compatible with the instruction set, ensuring seamless execution on modern IBM Z hardware while maintaining for legacy applications.

Middleware and Development Tools

IBM Z supports a robust middleware ecosystem that facilitates , database management, application serving, and messaging, enabling reliable enterprise operations on . Key components include IBM CICS Transaction Server, which provides high-volume (OLTP) for customer-facing applications, handling up to hundreds of thousands of s per second with built-in and . Similarly, (IMS) combines a hierarchical database manager with a transaction manager to support mission-critical workloads, processing billions of s daily while offering recovery features and integration with modern . IBM for z/OS serves as a Java EE-compliant middleware platform, hosting enterprise applications with support for , containerization via profile, and seamless integration across hybrid environments. For asynchronous communication, delivers reliable messaging across platforms, ensuring exactly-once delivery for business-critical data in multi-cloud setups, with clustering and replication tailored for IBM Z. Databases on IBM Z are anchored by Db2 for z/OS, a management system optimized for both OLTP and analytics workloads, capable of managing petabyte-scale data with sub-millisecond response times. It natively supports SQL standards for querying and for , enabling real-time analytics and integration with -driven applications without data movement. Development tools for IBM Z emphasize modernization and productivity, with IBM Developer for z/OS providing an Eclipse-based that supports languages like COBOL, , , and HLASM through features such as code navigation, debugging, and pipelines. The Edition extends this with VS Code integration and -assisted coding via watsonx Code Assistant for Z, which accelerates COBOL-to-Java conversions and generates automated tests using generative trained on mainframe expertise. Open-source support enhances flexibility, allowing Linux distributions like Ubuntu and Red Hat Enterprise Linux to run natively on IBM Z, leveraging the platform's hardware for high-performance computing. These distributions integrate Kubernetes for container orchestration, enabling deployment of cloud-native applications alongside traditional workloads through tools like Red Hat OpenShift on IBM Z. Integration with external systems is streamlined by z/OS Connect, which exposes z/OS applications and data as RESTful APIs with payloads, allowing mobile and applications to securely access IBM Z resources without custom coding. This facilitates architectures by supporting OpenAPI specifications and for scalable, governed interactions.

Security and Resilience

Hardware Security Modules

IBM Z systems incorporate specialized hardware security modules (HSMs) to provide robust cryptographic capabilities, with the Crypto Express adapters serving as the primary HSMs. These adapters, such as the Crypto Express8S, function as directly attached HSMs supporting the standard for cryptographic operations, including key generation, encryption, and digital signatures. They enable efficient handling of symmetric algorithms like for data protection in transit and at rest, while also supporting advanced features like tamper-resistant key storage. Recent advancements in these adapters extend to quantum-resistant cryptography, addressing threats from . For instance, the Crypto Express8S in IBM z16 supports the CRYSTALS-Kyber algorithm for key encapsulation, allowing secure key exchange resistant to quantum attacks, integrated via interfaces for seamless application use. This hardware acceleration ensures high-performance cryptographic processing without compromising , with keys generated and managed within the HSM's protected environment. Secure boot and trusted execution mechanisms form a foundational hardware root of trust in IBM Z, preventing firmware tampering from the earliest stages of system initialization. The hardware-based Root of Trust (RoT) anchors firmware integrity checks, verifying each component against cryptographic signatures before loading, thereby mitigating risks from malicious alterations. This extends to the (TEE), introduced in z13 and enhanced in later models, which isolates sensitive workloads in protected memory regions inaccessible even to privileged firmware or hypervisors. Data protection is further strengthened through pervasive , available since z14, which applies hardware-accelerated to data in flight and at rest with minimal overhead. Keys for this are stored in the Cryptographic Key (CKDS) and managed across cryptographic domains in the Crypto Express adapters, where each domain operates as an independent secure unit with its own master key. This domain isolation ensures that keys remain shielded, supporting granular control over encrypted datasets in CKD format without requiring application changes. IBM Z hardware security modules achieve high compliance standards, with Crypto Express adapters certified to Level 4, the highest level for physical and logical security, including tamper detection and response. This certification facilitates adherence to regulations such as GDPR for data privacy and PCI-DSS for payment card security, enabling organizations to process sensitive information in compliant environments. Innovations in the IBM z17 introduce an on-chip secure enclave leveraging isolated execution environments to protect AI models and . These hardware-enforced enclaves provide capabilities, ensuring that AI inference and training data remain encrypted and isolated from the host system, even during processing on the Telum II processor's integrated . This feature upholds data privacy while enabling secure AI workloads directly on the mainframe.

Availability and Recovery Features

IBM Z systems incorporate Parallel Sysplex, a clustering technology that interconnects up to 32 instances to function as a unified logical platform, facilitating centralized management, workload balancing, and enhanced availability without a . This configuration enables dynamic resource sharing and automatic redistribution of workloads across systems in the event of a failure, ensuring minimal disruption to operations. Reliability, Availability, and Serviceability (RAS) features in IBM Z emphasize proactive system health monitoring through environmental sensors that detect potential issues such as overheating or voltage anomalies before they lead to failures. Predictive , powered by these sensors and integrated diagnostics, allows for preemptive interventions, reducing unplanned outages and supporting overall system resilience. Additionally, IBM Z supports continuous via hot-swappable components, including processors, modules, and I/O adapters, which can be replaced concurrently without powering down the system, aligning with design goals for under two hours. For disaster recovery, IBM Z employs Geographically Dispersed Parallel Sysplex (GDPS), a solution built on Parallel Sysplex technology that automates replication and across multiple sites using and regional . GDPS enables near-zero recovery point objectives (RPO) by synchronizing data in , often achieving as low as five seconds or zero for specific workloads, while facilitating rapid site . This metro/regional approach supports both continuous availability within a site and robust across distant locations. The IBM z17 introduces enhancements to resilience, including IBM Z Flexible Capacity for Cyber Resiliency, which allows on-demand capacity upgrades during cyber incidents to maintain operational continuity without permanent hardware changes, and integrated capabilities for real-time detection and automated response as of z/OS 3.2 released in 2025. These features build on existing and GDPS to provide greater agility in hybrid cloud environments. IBM Z is engineered for "five 9s" availability, targeting 99.999% uptime, which equates to less than 5.3 minutes of annual unplanned downtime, with Parallel Sysplex and GDPS enabling failovers in seconds to maintain this level of service.

Applications and Integration

Industry Use Cases

IBM Z systems are extensively deployed in the financial sector, where they process a significant portion of global transactions. For instance, these mainframes support approximately 90% of all transactions worldwide, handling over $8.5 trillion in payments annually for networks like and , enabling real-time fraud detection through high-speed, secure processing capabilities. In government applications, IBM Z provides robust platforms for secure data handling. The U.S. (IRS) relies on IBM Z infrastructure for its core processing needs, including management and operations, having refreshed to the z16 model as of 2024. Similarly, the (SSA) utilizes IBM mainframes running to manage vast datasets comprising petabytes of critical records for benefits processing and administration. Healthcare organizations leverage IBM Z for maintaining HIPAA-compliant systems that safeguard sensitive patient information. These mainframes support electronic health records (EHRs) and billing processes with built-in and access controls to meet regulatory standards. For example, has historically employed on IBM Z to handle operational workloads, including data analytics for member services. In retail and airline sectors, excels at managing high-volume transactional workloads. Airlines such as use mainframes with the (z/TPF) for reservation systems, supporting rapid inquiry and booking operations across global networks. This setup enables thousands of (), ensuring reliable performance during peak demand. Energy and utilities companies depend on IBM Z for tasks like grid management and customer billing. These systems process massive datasets for power distribution and generating invoices, often integrated with like Db2 for efficient querying. One proof-of-concept deployment demonstrated billing support for up to 30 million customers, with a daily capacity of 1.5 million accounts in a 10-hour batch while optimizing for grid stability.

Hybrid Cloud and AI Capabilities

IBM Z facilitates hybrid cloud environments by integrating z/OS with through tools like z/OS Connect, which enables the creation and deployment of OpenAPI-compliant RESTful to expose z/OS applications and data without requiring application modifications. This integration supports seamless , allowing organizations to connect mainframe workloads to cloud-native services and extend legacy systems into hybrid architectures. Furthermore, IBM watsonx platforms enhance this connectivity by providing generative AI-driven assistance for development and modernization on z/OS, streamlining interactions between on-premises mainframes and cloud ecosystems. The IBM z17 mainframe incorporates the Telum II , featuring a second-generation on-chip designed for generative directly at the data source. This accelerator delivers up to 24 trillion operations per second () and supports decision-making, processing over 450 billion operations per day, representing a 50% increase compared to prior generations. By embedding capabilities within the processor, IBM Z reduces latency for workloads, enabling faster than traditional CPU-only processing while maintaining enterprise-grade and reliability. In practical applications, IBM Z supports analytics on mainframe data lakes, where transactional is processed in-flight to generate immediate insights without offloading to external systems. For instance, models trained on can detect fraud in transactions by analyzing every event in , leveraging the platform's high-speed access and integrated tools like IBM for . This approach ensures low-latency responses critical for high-volume financial operations, combining mainframe with cloud-based for enhanced accuracy. The IBM Z and Cloud Modernization Stack provides a unified for refactoring legacy applications into containerized formats, using Red Hat OpenShift Container Platform to bridge z/OS assets with hybrid environments. This stack enables developers to modernize COBOL-based applications into or containers, facilitating deployment across on-premises, , and edge locations while preserving mainframe performance. It supports full-stack development experiences, allowing teams to analyze, test, and integrate legacy code with modern tools for accelerated hybrid adoption. As of 2025, advances capabilities on IBM Z by providing enhanced support for acceleration technologies in the z17, including integration with agentic for operational simplification and productivity gains. This release introduces features for -driven management and observability, enabling organizations to deploy and monitor open-source large language models, such as variants of Meta's , directly on the mainframe for secure, on-premises inference. These enhancements align with hybrid cloud trends, allowing seamless scaling of workloads while leveraging 's robust .

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