Add DISP sub parameter options for CICS TDQ dynamic allocation

When defining a dynamically allocated CICS Extra Partition Transient Data Queue for output using dynamic allocation, the documentation at https://www.ibm.com/docs/en/cics-ts/5.5?topic=resources-tdqueue-attributes indicates three options are available for the "DISP" option - MOD, OLD and SHR. Of these only MOD allows any data already present to be retained with new data appended to the file.

This means an application can running in any one of a number of regions with each region opening and closing the queue as needed giving a single file of data but the file will keep growing unless a process exists outside CICS to delete all the records or redefine the dataset. A DISP of OLD or SHR would empty the file each time a region opened the Queue but this means the data has to be processed before another region opens the queue.

There is this statement under MOD "If CICS cannot find volume information for the data set on the DD statement, in the catalog, or passed with the data set from a previous step, it assumes that the data set is being created in this job step." However, it strangely then goes on to state "A data set allocated dynamically in this way is deleted when the queue is closed, and all records are lost."

I assume this deletion of a new dataset is because the default disposition sub parameters documented at https://www.ibm.com/docs/en/zos/2.5.0?topic=dp-defaults-3 are to to delete a new dataset and keep an existing one.

Changing CICS to always specify KEEP or CATLG for the sub parameters would be ideal but would be a change in behaviour.

Adding the ability to specify one or both sub parameters makes a disp of MOD even more useful as when processed, the data set can simply be deleted (or renamed as an archive) to be recreated by the next open.