On a system with extensive CCITCP/CCISSL activity, the generation of CAS9855I (connection) and CAS9861I (closing) messages may create significant spool/log usage.
To suppress the CAS9855I (connection) and CAS9861I (closing) messages you will need to add an ENVVAR DD to the CCITCP/CCISSL proc that points to a dataset which contains the following statement:
SUPPRESS_MESSAGES=1