Certain session protocols can prevent an application program from performing more than one transaction at a time on a single session. Using the parallel sessions function, you can enable an application program to engage in several sessions at once with the same logical unit. Thus, the application program can perform multiple transactions at the same time.

If you want an application program to have parallel sessions, you must authorize it by coding PARSESS=YES on the APPL definition statement. APPC=YES overrides PARSESS=NO to allow parallel sessions. The application program can distinguish sessions between the same LUs through the proper use of the communication identifier (CID).