The CICS region is referred to as a multiple-user single address space system (MUSASS). A MUSASS can process multiple sign-ons and units of work on behalf of multiple users in a single address space. A region logonid is used to validate accesses by the CICS address space. A region logonid record must specify MUSASS for it to be considered a MUSASS. The MUSASS attribute allows multiple users to sign-on concurrently to the region and permits the CICS interface to perform resource access validations on behalf of multiple users.
The MUSASS privilege can be added to a logonid using the TSO ACF command processor as follows.
CHANGE logonid MUSASS