Use the SELECT initialization statement to define scheduling controls you want associated with a particular job selection mode. The initial job selection mode is assigned to a JES3 main using the SELECT parameter on the JES3 MAINPROC initialization statement. If a MAINPROC statement does not indicate a selection mode, the SELECT statement default values are assigned to that main. Each select mode defined can be dynamically changed using the *MODIFY,G,main,S operator command. In addition, the commands *MODIFY,G,main,G or *MODIFY,G,main,C can indirectly affect the select mode. A SELECT statement must be specified for each select mode indicated on a MAINPROC statement or in a *MODIFY,G,main,S command.