SPACSECI—increase or decrease secondary allocation quantity (used with Allocation)
The primary role of the SPACSECI function is to increase the secondary allocation quantity as the file is being extended.
However, the SPACSECI function can also be used to decrease the secondary amount during an extend (see the PCTI RLST parameter).
The secondary allocation quantity is specified for a file to provide expansion space if the primary quantity is insufficient. To prevent overallocation on the data center’s disk drives, primary and secondary quantities are usually specified to handle normal conditions. However, during periods of unusually heavy activity, the secondary allocation might not be sufficient to allow the file to hold the extra data, causing the job to abend with a B37 or E37 system code.
When the PCTI parameter is not specified, SPACSECI increases the secondary allocation quantity of a data set at a user-defined point during secondary extent (see the SPACSECI parameter). The secondary quantity increase adds increasingly larger secondary extents to a data set and can prevent job abends due to out-of-space conditions.
When MVS adds a volume to a non-VSAM data set, the initial allocation made on the added volume will be equal to the size of the secondary allocation, not the primary.
There were two different ways of specifying the size of a secondary allocation. The traditional way is where SPACSECI increases the allocation by adding the value of the original secondary to a running total. The second way is by multiplying a percentage (via the PCTI parameter) times the original secondary.
With the addition of the new SQTY parm, you can now specify a fixed value to be used for each secondary on a volume.
In addition to increasing the secondary allocation amount for the next extent, the SPACSECI function also flags the data set for the release of unused space (as with the JCL parameter RLSE).
Release of unused space for a dataset can be controlled by specifying the parameter RELSPACE. RELSPACE=YES is the default. Release of unused space occurs at the close of dataset.
The following example shows how to create 10 cylinder secondary allocations starting with extent number 2:
INC DSN=TEST.DATASET
For more information, see: