Coding FREE=CLOSE or SPIN=UNALLOC in the JCL of a SYSOUT DD statement or specifying the DALCLOSE text unit key on a dynamic allocation (SVC99) parameter list for a SYSOUT data set causes JES2 to spin the data set for output processing when it is closed. JES2 then has the capability of performing output processing on the data set while the job continues execution. JESLOG data sets can be spun through $T J/S/T,SPIN.

In most cases, JES2 frees spool tracks allocated to the data set after printing, canceling, or transmitting the last copy of the data set.

For applications that dynamically allocate a spin SYSOUT data set (unallocation at Close - Key X'001C') but fail to issue FREE=CLOSE or SPIN=UNALLOC, JES2 does not free spool tracks allocated to the spin data set until the job is purged. In this case, end-of-task processing deallocates the data set and job purge processing returns the allocated tracks.