z/OS UNIX System Services Performance

This course describes and explains how to set up UNIX System Services (USS) to provide maximum performance benefits. This is a technical course that initially looks at the PARMLIB parameters that influence USS performance. It also provides advice in tuning the HFS and zFS file systems. This can provide significant performance benefits. The course also provides information on how USS work can be prioritised within the Workload Manager (WLM.)

This course is available 'on demand' (minimum 2 students) for public presentations and for one-company, on-site presentations.


On successful completion of this course you will be able to:

  • understand the basic features of UNIX System Services
  • exploit z/OS features that optimize USS performance
  • set up the BPXPRMxx parameters to optimize USS performance
  • set up the Workload Manager definitions for USS
  • tune the buffering for the HFS file systems
  • tune the buffering for the zFS file systems
  • migrate from HFS to zFS file systems.

Who Should Attend

This course is suitable for all Systems Programmers and Performance Analysts working in the zSeries Server environment. It is also suitable for USS administrators with a solid z/OS background.


Familiarity with UNIX System Services. This can be attained by attending the courses z/OS USS Part 1 - Concepts and Facilities and z/OS Part 2 - Configuration and Implementation. A good knowledge of z/OS is also required, so prior attendance on the course z/OS Concepts and Facilities (or equivalent experience) is required.


1 day

Fee (per attendee)

£475 (ex VAT)

Course Code



USS Features

UNIX internals overview; The Kernel; LOADxx and the IPL process; Load Unit Address; The Load Parameter - ddddxxsn; The LOADxx member; The UNIX support in z/OS; Displaying OMVS processes; The UNIX support in z/OS; Logging on to USS; Special TSO/E commands; Controlling z/OS UNIX - BPXPRMxx parmlib member; Displaying OMVS information; ulimit - a (shell command); New ISPF panels; The Shell; USS functions; Processes and fork(); fork() and shared storage; spawn() function; Inter Process Communication functions; Memory mapped files; Threads; Daemon processes; The UNIX file system; The system files - /etc, /dev, /bin and others; Display file systems;
Practical exercise 1.

USS Customising for Performance

VLF caching of UIDs & GIDs; USS RACF VLF parameters; Environmental variables; STEPLIBs; Storage consumption; USS region size; Exploiting LPA & LNKLST; Move executables into LPA; Binding executables into LPA; Shared object libraries; /etc/profile; $HOME/.profile; Customizing parmlib members; Controlling USS: BPXPRMxx parmlib member, BPXPRMxx - maximum sizes, BPXPRMxx - miscellaneous, BPXPRMxx - file systems, BPXPRMxx - network, BPXPRMxx - RESOLVER PROC, BPXPRMxx minimum values for Java?, Dynamically changing the BPXPRMxx options, BPXPRMxx - individual overrides; FILESYSTYPE buffer parameters; USS work; Why USS uses WLM; UNIX Services fork and spawn function calls; USS Service Classes; USS classification rules; Definitions for OMVS subsystem type work; Cataloged procedures used by USS; Customizing cataloged procedures; Performance enhancements using the VLF; Initial file system; HFS sharing; Extended file system; Version HFS - an example (1); System HFS - an example (2);
Practical exercise 2.

Hierarchical File Systems

Using files from UNIX programs; Managing UNIX files in z/OS; The Hierarchical File System; UNIX files and file systems; The Physical File System (PFS); The Logical File System (LFS); Device drivers; Directory structure; The root file system; The root file system z/OS; Shared file system; Mount points; Mounting file systems; Automount facility; Automount setup; Recommended file structure; Managing HFSs - confighfs; Confighfs: examples, -q Buffer Pool Statistics, /- root file statistics;
Practical exercise 3.

zFS File System

What is z/OS DFS zFS?; What are zFS file system aggregates?; Distributed File Service required for zFS; Sample Parameter File- IOE.SIOESAMP(IOEFSPRM); zfsadm shell command; zFS utility programs; zFS cache & performance; IOEPRMxx performance parameters; zFS performance data via an API; zFS performance data - zfsadm query; ZFS Cache: User & Metadata, Transaction & Log, Vnode; Directory Backing Cache; ZFS I/O by Aggregate; SMF records for USS; RMF reporting for USS; zFS Activity Report; zFS Summary Report; RMF Monitor lll reporting for USS; Allocating zFS aggregates; zfsadm format command; Migrating from HFS to zFS;
Practical exercise 4.

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