Overriding DBCTL generation parameters at execution time

You can change many IMS system definition values at DBCTL startup using parameters on the DBC procedure. You can specify these override parameters on the PARM of the EXEC statement. However, there is a 100-character limit to the length of the PARM field you can specify on a JCL EXEC statement, which means that you cannot override all possible DBC parameters in the JCL. A better approach is to use member DFSPBDBC, which allows you to specify DBCTL control region execution parameters that override those specified in the stage 1 macros.You can place several DFSPBDBC members in PROCLIB by replacing the member name DFSPBDBC with DFSPBxxx, where xxxmust be three alphanumeric characters. The RGSUF= keyword in the DBC procedure specifies the xxx suffix to be used during startup of the DBCTL control region. For more information about DFSPBDBC, see IMS: System definition.