z/OS I/O Monitoring, Tuning & Troubleshooting

This course gives technical support personnel in a z/OS installation a clear view and understanding of the tasks involved in z/OS performance management. As well as covering conceptual performance issues the course concentrates on the significant technical considerations of I/O tuning.

The RSM Professional Portal

All course attendees will be given free access to the RSM Professional Portal. This provides:

  • on-line access to the course notes (full colour, searchable and regularly updated)
  • access to the RSM Technical Forum.


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

  • explain what system performance requires
  • explain the role of a performance person
  • be able to implement I/O avoidance techniques
  • identify the component of an I/O which is causing a problem and suggest a remedy
  • implement caching effectively
  • optimise the functions of HSM
  • utilise RMF to tune MVS I/O
  • invoke performance enhancing features such as PAVs, DCM and I/O priority queuing
  • identify RMF information required for effective monitoring of I/O.

Who Should Attend

Technical support personnel who need to understand the performance aspects of z/OS systems.


A general understanding of z/OS features and functions.


2 days

Fee (per attendee)

£845 (ex VAT)

Course Code



What is Performance?

What is performance?; the performance issues; performance related activities; performance management; a transaction; transaction delay time components; measuring delays; MVS tuning and the Systems Programmer; three kinds of tuning; corrective tuning; preventive tuning; negative tuning; knowing your system.


Data spaces and hiperspaces in MVS; Data Space & Hiperspace use in MVS; VLF, LLA, DLF and Hiperbatch; VLF and DLF; what is VLF?; setting up VLF; VLF macros; example of VLF parameters; what is LLA?; running LLA in MVS; LLA module staging; example of LLA parameters; Data Lookaside Facility and Hiperbatch; using DLF and Hiperbatch.

Exploiting Coupling Facilities

Exploiting the Parallel Sysplex; Parallel Sysplex exploiters; old functions, new techniques; the 'real' parallel sysplex; workload distribution; exploiters; WLM and dynamic networking; VSAM Record Level Sharing; CICS VSAM file accessing applications; IGDSMSxx RLS Parameters; RACF and Sysplex; sysplex wide DAE; Global Resource Serialization (GRS); GRS Fully Connected Complex and Sysplex; GRS Star; GRS Star setup definitions; Star configuration RNL management; Sysplex related JES features; JESXCF facility; Communication via JESXCF; VTAM exploitation; Generic Resources requirements; CICS exploitation; TSO generic resources; Batch in a Parallel Sysplex with WLM; what WMB does not do... ; what WMB manages; DB2 exploitation ; IMS exploitation; TSO/E and SYS1.BROADCAST.

Input/Output Processing

Why I/O processing?; what is I/O?; MVS support for I/O processing software; MVS and I/O processing; Application I/O; the application program; the DD statement; going to the Access Method; the Access Method; getting the channel program started; EXCP - an IOS Driver; IOS 'Front End'; actually starting the I/O; the I/O engine at work; the Channel Sub-System (CSS); Hardware System Area (HSA); "The I/O Farm"; the I/O Interrupt; IOS Post processing; back to the Access Method; the I/O process from A to Z; starting the I/O; going back from starting the I/O; I/O complete; caching concepts; Read Hit; Write commands; Write Hit; Read Miss; Write Miss; cache modes; review questions - Input/Output processing.

HSM Performance

DFHSM start-up procedure; DFHSM start-up options; defining Control Data Sets; Multicluster Control Data Sets; VSAM Record Level Sharing (RLS); requirements for CDS RLS serialisation; implementing RLS mode; Control Data Set performance summary; general HSM performance summary; monitoring DFHSM; Common Recall Queue; enabling CRQ; activating CRQ - SETSYS COMMONQUEUE; Migration/Recall performance; SDSP performance summary; logging; log contents; ARCPRLOG output; ARCPEDIT output; REPORT command; REPORT daily statistics; REPORT volume statistics; HSM exercise.

Hardware I/O Performance

FICON Technology; MIDAW; Media manager; IOSQ time problem; overcoming restrictions; multiple allegiance and Parallel Access Volumes; PAV and cache; HiperPav; PAV RMF support; managing PAVs; what are PAV limitations?; Intelligent Resource Director (IRD); IRD LPAR CPU management; IRD LPAR CPU management (2); Dynamic Channel Path Management (DCM); DCM requirements; DCM definitions and concepts; configuring DCM; RMF Channel Path Activity report; DCM and the I/O queueing report; I/O priority prior to IRD; I/O priority queuing; WLM I/O priority management; UCB & DASD CU I/O priority; CSS I/O priority; enabling Channel Subsystem Priority Queuing; review questions.

RMF Reporting

Resource Measurement Facility; CACHE - Cache Subsystem Activity reports; CHAN - Channel Path Activity report; DEVICE - device activity report; Monitor I shared DASD; Monitor I shared tape activity report; FCD - FICON director activity report; IOQ - I/O queuing activity report (1); PAGESP -Page/Swap data set activity report; PAGING - Paging activity reports; VSAM RLS activity by storage class; VSAM RLS activity by data set; RMF I/O performance exercise.