Statement summary

Table 1. MAINPROC Summary
Variable	Value
Required/Optional Statement	Required
Statement Default	None
Placement in Initialization Stream	This statement must follow the ENDJSAM statement.
Coding Considerations	The SELECT parameter on this statement must correspond to the NAME parameter (specified value or default value) of a SELECT statement. The SPART parameter on the MAINPROC statement must correspond to the NAME parameter on a SPART statement. The MAXSYSTEM value for any sysplex couple data set should be equal to or greater than the total number of mains that are defined by the MAINPROC statement.
Security Usage	None
Performance Considerations	None
Initialization Stream Overrides	The TRKGRPS parameter specification on the SYSOUT and CLASS initialization statements and on the //*MAIN JES3 control statement override the TRKGRPS parameter specification on the MAINPROC initialization statement.
Restart or Command Modification	Warm start, cold start, or hot start with refresh for all parameters. Do not change the sequence of MAINPROC statements during a hot start with refresh. However, you can add or delete statements at the end of the sequence, or you can rename an existing MAINPROC statement to a new one without changing the order of any other existing MAINPROC statements. Use a cold start to change the sequence of MAINPROC statements. Although JES3 will not prevent you from changing the sequence of MAINPROC statements during a warm start, this is not recommended and will in some cases cause undesirable side effects. For example, a job could run on a system other than the system or systems for which it is intended. If you do make this change, evaluate how a change in sequence will affect your operations, for example, consider things such as: Whether there are any jobs in pre-execution at the time you perform the warm start or if all jobs in the job queue are in output service. Whether groups and classes have special main limitations or whether they are defined such it does not matter where a job in the class or group runs. Whether jobs exist that indicated the processors to be used to execute the job by specifying the SYSTEM or SYSAFF parameter on the MVS JOB statement or the SYSTEM parameter of the JES3 //MAIN JECL statement. Whether you have any user modifications that depend on the MPC sequence number. You can also use the `MODIFY,G,main,SELECT,MODE,m` command to change the "select mode" for a MAINPROC. The global processor cannot be deleted during a hot start with refresh. If you attempt to do this, an error message is issued and JES3 initialization ends. If you IPL and start JES3 on a processor that is not currently defined by a MAINPROC statement, you can add the processor with a hot start with refresh only if you do not intend to bring it up as the global at the same time. If you do intend to make it the global, you must perform a warm or cold start. Alternatively, you can perform a Dynamic System Interchange (DSI) to temporarily make an existing processor the global, add this processor as a local, and then perform a DSI to this processor after it has been added. During a hot start with refresh, the parameters PRTPAGE and FIXPAGE cannot be changed unless the processor described by the MAINPROC statement is IPLed. During a hot start with refresh, if any MAINPROC statements are added, deleted, or changed, all processors that are below the z/OS® 1.4.0 JES3 level must be IPLed.