Modifying JES2 initialization statement specifications

If you are restarting JES2 for the purpose of changing initializationstatements or parameter values, a cold start is only required for a limited number of JES2 parameters. A warm start can often be used for most parameters, or a specific $T operator command might suffice. The level of minimal JES2 disruption and operator intervention is listed for each JES2 initialization parameter under the heading ‘Modification:’ within the full parameter descriptions in z/OS JES2 Initialization and Tuning Reference. Study these before restarting JES2 for the purpose of initialization parameter specification modification. You might be able to avoid a JES2 warm or cold start. The modification heading is listed for all parameters on all statements; it is specified as follows, with the minimal intervention level:

Table 1. Modification Heading
Minimal Modification	Meaning
COLD START	Only a cold start can be used to modify this parameter.
WARM START	A warm start is required to modify this parameter; a cold start can be used. (To understand the different types of warm starts, see Restarting JES2.)
Operator Command	This parameter can be modified by a specific $T operator command. See z/OS JES2 Commands for a full description of the $T command. This parameter might, or might not, also be modifiable by any type of WARM start, or a COLD start. (Some parameters can be modified only by $T command or cold start; these are noted within the parameter descriptions in z/OS JES2 Initialization and Tuning Reference.)

Most JES2 initialization parameters can be displayed by the $D operator command. Particularly for tuning purposes, the operator can ask JES2 for the current setting of many JES2 parameters. In this manner, both the operator and the system programmers can be aware of the JES2 environment.

Dynamic display and modification of the JES2 initialization parameters can be used to ease the tuning of your MVS™ system without unnecessarily disrupting system processing and decrease your installation's need for planned system outages.