OS/390 Parallel Sysplex Configuration, Volume 2: Cookbook

For more information about structure full monitoring and Auto Alter support,

refer to

OS/390 MVS Setting up a Sysplex

, GC28-1779.

Table 14 (Page 2 of 2). Auto Alter Exploiters

Product/structure

IMS IRLM Lock

IMS OSAM Cache (in IMS V6 + APAR PQ38946)

IMS VSAM Cache (in IMS V6 + APAR PQ38946)

MQSeries Shared Queues

System Logger

WLM Multisystem Enclaves

XCF Signaling

Note:

1) Support is being added to IMS/ESA V6 to support Auto Alter of the

entry/element ratio for these structures.

2.2.2 Using Central and Expanded Storage for the CF

The storage supporting CFCC can consist of both central storage (CSTOR) and

expanded storage (ESTOR). However, using both types of storage complicates

structure space planning and CSTOR/ESTOR configuration.

In a 9674 C02/C03, little overhead results from using expanded rather than

central storage. In a 9674 C04 and follow-on CFs, the overhead is even smaller.

However, you are only likely to want to use ESTOR if you require a CF partition

with more than 2 GB of storage.

Recommendation about CSTOR/ESTOR

Always use CSTOR for the CF before using ESTOR. For 9674-C02 and later

CFs, define all storage up to 2 GB as CSTOR. Define ESTOR only if your CF

partition requires more than 2 GB of storage.

Certain entire structure types or structure components can

only

reside in what

CFCC refers to as control storage (which is composed only of CSTOR). Other

structure components can reside in either control or non-control storage (which

is composed of ESTOR). Only the “data elements” for cache structures and the

“list elements” for list structures can reside in ESTOR. All other structure

components

must

reside in CSTOR. For example, the following items must

reside in CSTOR:

All lock structures

List structure headers, list entries, list lock table, and internal control blocks

related to the list structure

Cache structure directory entries and internal control blocks related to the

cache structure

When a structure is allocated that has components that can reside in non-control

storage, then non-control storage is preferred over control storage for those

components. If there is insufficient non-control storage for these components,

the entire structure is allocated from control storage.

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Parallel Sysplex Configuration, Volume 2: Cookbook