Specifying CICS options through the IDIOPTS DDname

To avoid the need to recycle CICS® in case compiler listing or side file data sets change, specify these via the DataSets option in a user options file that is pointed to by the IDIOPTS DDname. For details, refer to DataSets and User options file IDIOPTS.

It is also better to use the IDIOPTS DDname pointing to a data set and containing: 
DataSets(IDIHIST(history-file-dsn))
than to use the following statement in the CICS® JCL:
//IDIHIST DD DISP=SHR,DSN=history-file-dsn
If you use 
//IDIHIST DD DISP=SHR,DSN=history-file-dsn
then JCL allocation holds an ENQ on the history file data set name for the full time when CICS® is running. However, if you use 
DataSets(IDIHIST(history-file-dsn))
then the allocation is dynamically obtained and released when required by Fault Analyzer. As a result, history file maintenance and renames can be done while a CICS® system that has written to it is still running. The 
DataSets(IDIHIST(history-file-dsn))
option can even be changed to point to a new history file while CICS® is running and takes effect when the next fault entry is created.

The IDIOPTS data set used must be a PDS or PDSE to permit update using ISPF EDIT while CICS® is running.