Using Overrides with Alternate Index

When using IAM data sets with alternate indexes and paths, the DSN= parameter must be used, instead of the DD= parameter. This is because the actual IAM data sets that are used will be dynamically allocated with system generated DD names, so the DD names are not known in advance. The only meaningful override for a PATH is the trace information. If tracing is specified for a PATH, tracing will be propagated to all of the data sets opened because of the PATH open. Other overrides on the PATH will be ignored.

The example below shows how to specify an override for a base cluster and an alternate index, which are being accessed via a PATH. The override for the base cluster will specify a MAXBUFNO value, while the override for the alternate index is using the IAM Dynamic Tabling feature. Use of dynamic tabling on the alternate index will provide a way to keep the alternate index in virtual storage, if it is not too large, and if it is being randomly accessed.

Example 6: Overrides when using a Path

Example of Overrides with an IAM Alternate Index