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WebSphere Application Server for z/OS

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IBM WebSphere Application Server for z/OS
Company typeSoftware
IndustrySoftware, Middleware
ProductsWebSphere Application Server
ParentIBM

IBM WebSphere Application Server for z/OS represents a critical deployment within IBM's WebSphere Application Server suite, with the most recent version being 9.0.

Although the open standard interfaces supported by WAS remain uniform across different platforms at matching version and release stages, the core functional implementations vary to capitalize on each platform's distinctive capabilities while maintaining a consistent programming interface.

Exploiting the WAS z/OS Platform

WebSphere Application Server for z/OS Version 7 harnesses numerous features unique to the platform:

  • WLM—for transaction categorization, workload routing, server scaling, and resource distribution
  • SAF—security enforcement through solutions such as IBM’s RACF via the SAF interface
  • Cross-memory communication—facilitates shared memory buffer exchanges essential to WebSphere Optimized Local Adapters
  • SMF—WAS z/OS generates SMF 120 records, including the advanced 120 subtype 9 introduced in Version 7
  • RRS—manages global synchronization points for two-phase commit transactions
  • zAAP—leverages specialized processors dedicated to Java workloads, enhancing cost-effectiveness

Version 7.0 "z Differentiators" ("zDiff")

The release of Version 7.0 brought five "zDiff" capabilities that distinctly utilize the z/OS environment:

  • New SMF 120, Subtype 9 — a consolidated SMF record offering enhanced transparency into each request and response cycle
  • Optimized Local Adapters — expands cross-memory communication beyond WAS z/OS application servers, enabling two-way invocation of EJBs and integration with external systems like CICS and Unix System Services
  • FRCA (Fast Response Caching Accelerator) — a TCP/IP stack cache mechanism functioning as an external cache provider for WAS DynaCache, streamlining request processing by minimizing code execution paths when cached objects exist
  • Thread Hang Recovery — improves JVM management by interrupting stalled threads or deferring EC3 abends through configurable thresholds, thereby boosting stability and performance under heavy CPU load
  • DCS/XCF — shifts Distributed Consistency Services signaling from TCP/IP to System z Parallel Sysplex’s XCF facility, optimizing communication efficiency within WAS cells on z/OS platforms

Version 8.0 "z Differentiators"

Version 8 of WebSphere Application Server for z/OS introduced the capability to configure server behavior on a per-request basis, enhancing the existing WLM classification file that assigns WLM transaction classes. V8 added new XML tags to specify behaviors for individual requests.

Important XML tags comprise:

  • dispatch_timeout – defines the timeout in seconds starting from when a request enters the WLM queue until completion
  • queue_timeout_percent – specifies the timeout as a percentage of dispatch_timeout indicating how long a request may remain in the WLM queue before timing out
  • request_timeout – sets the timeout in seconds for outbound IIOP requests directed to EJBs on other servers
  • stalled_thread_dump_action – determines the action taken when a thread is stalled due to timeout (options include svcdump, javacore, heapdump, traceback, javatdump, none)
  • cputimeused_limit – CPU time limit in milliseconds after which a request thread’s WLM enclave is quiesced, reducing its priority
  • cputimeused_dump_action – specifies the action triggered when CPU time limit is exceeded (same options as stalled_thread_dump_action)
  • dpm_interval – interval in seconds at which the Dispatch Progress Monitor (DPM) initiates dump actions
  • dpm_dump_action – action executed at every dpm_interval (same set of options as above)
  • SMF_request_activity_enabled – activates SMF 120.9 recording for the request
  • SMF_request_activity_timestamps – enables recording of SMF timestamps
  • SMF_request_activity_security – activates SMF security detail logging
  • SMF_request_activity_CPU_detail – enables detailed SMF CPU usage recording
  • classification_only_trace – turns on tracing exclusively for the specified request at the server’s detail level
  • message_tag – applies a custom tag (up to 8 bytes) to all trace and log entries associated with the request
  • timeout_recovery – defines recovery behavior upon timeout: servant initiates normal EC3 abend processing; session closes TCP/HTTP session and returns an error response to the client

These improvements provide finer control over request processing, supporting enhanced performance tuning and troubleshooting within enterprise settings.

Version 8.5

Announced on April 24, 2012, WebSphere Application Server Version 8.5 introduced the Liberty Profile runtime, a modular web container server designed with the ability to perform dynamic updates.

Integration of Liberty Profile with z/OS platform features

Liberty Profile on z/OS incorporates enhancements that take advantage of specific z/OS capabilities:

  • SAF – Integrates with z/OS Security Access Facility to handle user authentication and serve as a keystore/truststore for managing digital certificates.
  • WLM – Utilizes the z/OS Workload Manager to categorize workloads into distinct enclaves, supporting separate WLM reporting classes for detailed resource consumption monitoring.
  • JDBC Type 2 with RRS – Connects to IBM DB2 through a cross-memory interface; global transaction coordination is managed by IBM Resource Recovery Services.
  • MODIFY – Supports the use of the z/OS MODIFY command to trigger and control SVC and transaction dumps associated with specified servers.
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