Initializing JES3

Each time JES3 starts, initialization occurs. During initialization, MVS™ runs the JES3 cataloged procedure. The JES3 cataloged procedure is JCL that causes MVS to allocate the data sets required by JES3. Depending on the type of start specified, JES3 will process the JES3 initialization stream, thus initializing itself.

You can tailor JES3 by:

Modifying the JES3 cataloged start procedure
Modifying the JES3 initialization stream
Using a segmented initialization stream
Creating and using an alternate initialization stream
Coding a program for installation exit IATUX15. An installation exit is a part of JES3 specifically designed for installations that want to augment or change JES3 processing. For a description of this and other exits, see z/OS JES3 Customization.
Dynamically reconfiguring JES3