If a request is received from an application with an SNA Begin Bracket, and the session is already in a bracket, then this parameter specifies whether or not the request will be rejected with a negative response.
This common session parameter is applicable to these control statements: SYSTEM (see SYSTEM statement), PROFILE (see PROFILE statement), USER (see USER statement), TERMINAL (see TERMINAL statement), and APPL (see APPL statement).
If the value is set to Yes then the request will be rejected by sending a negative response containing a 08130000 sense code.
The default behavior (or if REJBB is set to No) for this eventuality is to accept the request and, if required, send a positive response with no sense code.
See also the s_rejbb session variable, as documented in the Panels, Scripts and Variables manual.
If updated, changes are applied at the next session start.