Controlling offload devices

JES2 provides commands you can issue for:

Starting an offload device
Draining an offload device
Halting an offload device
Setting offload data set characteristics

Starting an offload device: When an offload device is started, any associated transmitters/receivers that have been started, will become active. If the offload device is already in use on any member in the multi-access configuration, JES2 denies the start and the $HASP593 message is issued. If the corresponding data set is already in use by another offload device, JES2 denies the start and issues the $HASP614 message.
Draining an offload device: The current job completes processing before the device is allowed to drain. This draining process stops the selection process for associated transmitters and receivers that are currently active. When the device is drained, JES2 closes and deallocates the offload data set.
If you issue the $P OFFn.xx (where xx is JT, JR, ST, or SR) command for an offload device that has been halted ($Z) during the receive operation, you may need to restart the reload operation to finish the job that was halted. Then the device will drain.

Note: On the receive operation, the offload device is automatically drained when an end-of-file is encountered.
Halting an offload device: Halting an offload device does not cause the offload data set to be deallocated, but the selection process for active transmitters and receivers is automatically stopped so that the operator can reset the work selection criteria before restarting the transmit or receive operation.
If you issue the $Z command during the transmit operation, any active transmitter(s) will finish processing their currently active jobs before the selection process is halted. If you issue the $Z command during the receive operation, any active receivers will be halted immediately in the middle of the jobs being processed. When the receive operation is restarted, the offload device will begin to read the offload data set at the point where it was halted.
Displaying the status of an offload device: You can display detailed information about a specific offload device ($D OFFLOAD(n)), or about all offload devices defined to JES2 ($D U,OFFS). Unless you request limited status information, the status of all corresponding transmitters and receivers is also displayed.
Setting offload data set characteristics: You may set offload data set characteristics only if the indicated offload device is drained.If you are uncertain of the characteristics in effect, you may display the characteristics for the offload device in question. Use $D OFFLOAD(n) to display detailed information about an offload device; use $T OFF(n).xx,WS= to set offload data set characteristics.