What are the pros/cons for a site in using the Sysplex Coupling Facility for the ACF2 databases versus the ACF2 Cache Facility?

book

Article ID: 35453

calendar_today

Updated On:

Products

CA ACF2 CA ACF2 - DB2 Option CA ACF2 for zVM CA ACF2 - z/OS CA ACF2 - MISC CA PanApt CA PanAudit

Issue/Introduction

Question:  

What are the pros/cons for a site in using the Sysplex Coupling Facility for the ACF2

databases versus the ACF2 Cache Facility?

Answer: 

Key points regarding the ACF2 Cache Facility versus the Sysplex Coupling facility. 

 

The XES data sharing feature lets the customer define structures in the 

SYSPLEX that multiple systems can use. These structures contain data to be 

shared between these systems. Once the data has been placed in the structure 

it is valid to be read, updated, or deleted by any system connected to that 

structure. 

 

The purpose of putting ACF2 records in the sysplex coupling facility is to 

minimize I/O. I/O to the RULES and INFOSTG databases can be minimized by 

making commonly used rules and profiles resident in storage via the INFODIR 

record. That leaves only the logonid records from the LID database as being 

a source for significant I/O. Generally, since there is more READ I/O than 

WRITE I/O, and since RESERVEs are only issued for WRITES, if you put the lid 

records in the SYSPLEX coupling facility where they are available for READs, 

there would only be I/O to the database when they are updated. 

 

Most clients only specify lids in the coupling facility since they make 

commonly used rules and profiles resident in storage via the GSO INFODIR

as RESRULE records.

 

Performance would have to be measured by one of the generally available monitors,

such as MAINVIEW and OMEGAMON. CA does not provide a performance measurement

tool applicable to SYSPLEX coupling. 

 

XES Coupling Facility Advantages: 

- Records are kept in a Coupling Facility structure 

- No database ENQ by requestor 

- I/O is processed concurrently 

 

Considerations: 

- Its only used for individual read requests 

- Read for update and sequential processing is ignored ** 

- Requires use of the Coupling Facility 

- Limited to the speed of the Coupling Facility device 

 

** Any read for updates to a logonid record are done to the database before the 

update occurs in the Coupling Facility. A sequential read such as a TSO, 

ACF, LIST like(mask) would be done to the database rather than to the 

Coupling Facility. 

 

ACF2 Cache advantages: 

- No need for special hardware or software 

- I/O processed concurrently 

- No waiting on write requests 

- Records kept in the ACF2 address space 

- No database ENQ by requestor 

 

Considerations: 

- Sequential processing 

- Requires GSO SYNCOPTS when sharing the database 

 

At this point it is difficult to say one is better than the other. Every 

site's environment is different, we recommend that a site evaluates their 

configuration and system performance to determine which tool will best 

suit their needs. 

 

Additional Information:

Details on the ACF2 Cache Facility and the SYSPLEX Coupling Facility can be found in the 

CA ACF2 for z/OS Administration Guide in Chapter 12: Maintaining Cache Records and 

 

Chapter 24: Using the SYSPLEX Coupling Facility.

 

Environment

Release:
Component: ACF2MS