You might experience short-on-storage conditions in 24-bit
storage or 31-bit storage despite increasing the DSALIM or EDSALIM limits,
respectively. In this situation, you might need to enable the CICS® self-tuning
mechanism. It is also possible to fix the size of each individual
DSA by using the corresponding SIT override.
About this task
Use the self-tuning mechanism and the SIT overrides only if increasing the
DSALIM or EDSALIM limit does not completely resolve the
short-on-storage problems.
Allocating into managed extents can result in a block of storage in an extent that is
insufficient to satisfy a GETMAIN request. With the dynamic nature of the subpools and DSAs, this
situation will probably resolve as the extent storage is reused. If you specify the initial DSA size
using the SIT override for the affected DSA, CICS reserves
contiguous extents up to the amount specified, and eliminates the blocks of storage.
Tip: Define MAPS as MAPS. If you defining MAPS as programs, they are loaded into LDRES
rather than into LDNUC. LDRES is part of the SDSA and is more sensitive to fragmentation.
Procedure
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You can add records to the local catalog to enable the CICS self-tuning mechanism for storage
manager domain subpools.
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You can fix the size of one or more individual DSAs by using the corresponding SIT overrides
(CDSASZE, UDSASZE, SDSASZE,
RDSASZE, ECDSASZE, EUDSASZE,
ESDSASZE, and ERDSASZE).
To determine the values to use, follow this process:
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Collect DFH0STAT output for information showing storage use by each DSA during the
intervals.
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Review the CICS
statistics for several days.
The statistics provide information that you can use to define the amount of storage used at a
subpool and a DSA level. Extent usage is shown with the number of extents added and released.
In addition to the DSA information provided in DFH0STAT, the results about each subpool are
provided, including the DSA where it was allocated. If statistics are being gathered, end-of-day
statistics only provide data since the last statistics collection.