1. Job mask suppression is in effect for this exit.
2. Bit 7 of the response byte is set based on the setting of SSALSPIN in the SSOB: If SSALSPIN is on, bit 7 is set on. If SSALSPIN is off, bit 7 is set off.
3. By examining the setting of bit 7 in the response byte and the setting of IOT1SPIN in IOTFLG1, you can determine if the data set was originally allocated as spin and how it was unallocated:

   Bit 7	IOT1SPIN	JES2	DATA SET
   on	on	Spins the data set	The application allocated the data set as spin.
   on	off	Spins the data set	The application allocated the data set as non-spin (either DALCLOSE was not set in dynamic allocation or FREE=CLOSE was not specified on the DD statement). The application used dynamic allocation to unallocate the data set.
   off	on	Does not spin the data set	The application allocated the data as spin but the task terminated before closing the data set.
   off	off	Does not spin the data set	The application allocated the data set as non-spin and the data set remains non-spin.

4. Expanding the JCT Control Block

If the $JCT address is contained in field SJBJCT, you can add, expand, locate, or remove extensions to the job control table ($JCT) control block from this exit using the $JCTX macro extension service. For example, you can use these extensions to store job-related information. For more information, see z/OS JES2 Macros