Endevor implications of NON_VSAM_XTIOT=YES setting

Products

• Endevor

Issue/Introduction

Planning to change NON_VSAM_XTIOT parameter in DEVSUPxx member in SYS1.PARMLIB from NO (default value) to YES

This setting is intended to enable support for XTIOT, uncaptured UCBs, and DSAB above the 16 MB line in BSAM, BPAM, and QSAM access methods which is discussed in IBM manual z/OS DFSMS Using Data Sets. By default, these features are only supported for VSAM and EXCP access methods.

What would be the implications of this change for Endevor?

Resolution

The IBM documentation states that:

• Datasets allocated via JCL don't use these features. They need to be explicitly requested when performing dynamic allocation of datasets
• Programs request these features by setting flags S99TIOEX, S99ACUCB or S99DSABA in the DYNALLOC request
• Programs that dynamically allocate datasets using any of these features or that handle datasets that may have been dynamically allocated by other programs using these options need to be adjusted in order to support them.

Endevor indeed performs many dynamic allocations of datasets. However, it does not request any of these features in its DYNALLOC requests.

Therefore, Endevor itself is NOT affected by this change.

There is, however, a small possibility of conflict if:

• The site uses an user exit 04 (file exit) which validates and optionally changes the dataset requested by the user in ADD, UPDATE or RETRIEVE actions. This user exit is normally not used.
• The exit decides to change the dataset to be used in the action (which requires the exit to dynamically allocate the dataset and return the DD name to Endevor)
• The exit requests some of the above features when dynamically allocating the dataset

This situation is VERY unlikely but might happen anyway and has never been tested.