Assigning devices dynamically after initialization

After initialization, operators can use JES2 commands to add, assign, or reassign local printers, punches, readers, communication lines, and channel-to-channel (CTC) adapters. By specifying a device statement without a unit value, the device name and its attributes become known to JES2, but a physical device is not assigned until a unit value is added using a JES2 $T command. Defining devices in this manner allows installations to dynamically assign or reassign devices after initialization.

You can omit the UNIT= on the following JES2 device initialization statements:

PRT(nnnn)
PUN(nn)
RDR(nn)
LINE(nnnn)

If you do not specify UNIT= on the PRT(nnnn) statement, JES2 bases the defaults for COPYMARK, FLash, FCB, and UCS on the MODE= parameter. If MODE=FSS, these parameters default to specifications for a non-impact printer. If MODE=JES, these parameters default to specifications for an impact printer. To determine how JES2 parameters affecting FSS printer characteristics retain values across a hot start, see Functional subsystem reconnection.

During initialization, JES2 does not allocate or assign devices defined by these spare device statements. JES2 starts FSS printers with a valid FSS procedure whether or not UNIT= has been specified. After initialization completes, operators can dynamically assign or reassign a physical device by specifying the UNIT= parameter on any of the following commands:

$T RDR(nn)
$T PRT(nnnn)
$T PUN(nn)
$T LINEnnnn

Operators can dynamically assign as many local printers through the $ADD PRT(nnnn) command. However, dynamically assigned devices are saved across a JES2 hot start only.

Note:

To define a device to JES2 permanently, installations must specify a value on the UNIT= parameter in the initialization stream.
You must first drain a device before replacing it.
You can dynamically add a local printer (JES2- or FSS-managed) using an $ADD PRT(nnnn) command. You do not need to define spare initialization statements to allow the dynamic addition of printers when using the $ADD command.
If your installation is using Print Service Facility (PSF)^* Version 1.4 or an earlier release of PSF, only those local FSS printers that have been defined to the base control program as installation-static can be dynamically assigned to JES2 using $T commands.

See z/OS JES2 Commands for additional information about dynamically assigning or reassigning local devices using $T commands.