7.1 Modifying JES2 You can change JES2 initialization parameter settings through six methods that vary in their impact to the JES2 member. The following list provides the hierarchy, beginning with the easiest and least disruptive method, and ending with the most difficult or disruptive method for the JES2 member: 1. Operator command JES2 provides commands that permit you to dynamically change nearly all the JES2 attributes that are defined in the JES2PARM member. This is the least disruptive way to make a change to JES2. However, you must remember to reflect your change back into the relevant JES2PARM member in order to ensure that the change is not lost the next time JES2 is started. 2. Hot start A hot start is performed when JES2 abnormally terminates (or is stopped using the $PJES2,ABEND command) and is subsequently restarted using PARM=WARM, and JES2 determines that an IPL has not occurred prior to restart. You can use a hot start when JES2 has stopped, but other jobs and started tasks have continued to function and have not experienced problems. When you hot start JES2, all address spaces continue to execute as if JES2 had never terminated. Functional subsystems will continue to process spooled output as long as possible before the hot start, and JES2 will reconnect to the functional subsystem (FSS) during the hot start. Hot starts do not affect other members in a multi-access spool configuration. Note that many parameters in the JES2PARM deck are ignored by JES2 when coming up with a hot start. For more information, refer to z/OS JES2 Initialization and Tuning Reference, SA22-7533.