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.
76
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