Space allocation

Allocate spool data sets as single-extent data sets; if you allocate additional extents, JES2 uses only the first extent for spool space. Each spool volume must contain a data set named SYS1.HASPACE (unless the DSNAME= parameter on the SPOOLDEF statement specifies another name) in order to be used as a spool volume.

Note: JES2 supports using a data set more than 64K tracks in size based on the SPOOLDEF LARGEDS= parameter. If LARGEDS=FAIL is specified, the SYS1.HASPACE data set has to be less than 64K tracks in size. Specify LARGEDS=FAIL to allow pre-z/OS 1.7 levels of JES2 to co-exist in an MAS. If you no longer have any pre-z/OS 1.7 members in your MAS, you can specify LARGEDS=ALLOWED to create SYS1.HASPACE data set up to 1,048,575 tracks.

The unit of direct-access space allocation for JES2 is the track group. Obtain the number of tracks in a track group is obtained by the following formula:

Number of track / track group = TGSIZE on SPOOLDEF stmt
                                _______________________
                                   buffers per track

where: TGSIZE=number of buffers in a track group, and buffers per track is detailed in Table 1based on BUFSIZE and device type.

You can allocate spool space by using any valid space specification, but keep the following considerations in mind:

To minimize unused DASD space, you should allocate spool space contiguously, because JES2 only uses the first extent of the spool data set.
The spool allocation must be equal to or greater than the number of tracks in a track group.
TRK (track) allocations waste less DASD space than CYL (cylinder) allocations, because you can specify the allocation as an integral multiple of a track group.

For further information concerning the JCL SPACE parameter and its syntax, see z/OS MVS JCL Reference.

An example of defining spool data sets appears in Figure 1.

For multi-access spool configurations, all spool and checkpoint volumes must reside on devices that have at least one channel path to each JES2 system in the multi-access spool environment. If the multi-access spool configuration is a member of an NJE network, NJE commands and messages sent among JES2 systems attached to the shared spool are queued on the spool volume. To calculate the number of track groups normally needed in SYS1.HASPACE for NJE messages, use the following formula:

                               n² + n³
    Number of track groups  =  ───────
                                  2

where n is the number of JES2 subsystems attached to the shared spool.

Figure 1. Example of defining and allocating the JES2 SYS1.HASPACE data set

//ALLOCATE JOB  (...),'PREPARE FOR JES2',MSGLEVEL=1
//ALLOCAT  EXEC PGM=IEFBR14
//*
//SPOOL1   DD   DSN=SYS1.HASPACE,UNIT=3390,
//              VOLUME=SER=SPOOL1,DISP=(NEW,KEEP),
//              SPACE=(CYL,884,,CONTIG),DCB=(DSORG=PSU)
//*
//SPOOL2   DD   DSN=SYS1.HASPACE,UNIT=3390,
//              VOLUME=SER=SPOOL2,DISP=(NEW,KEEP),
//              SPACE=(TRK,13256,,CONTIG),DCB=(DSORG=PSU)
/*

Figure 2. Example of allocating and formatting a SPOOL volume before starting it

This job assumes a record size (SPOOLDEF BUFSIZE=) of 3992. For other buffer sizes, replace the two occurrence of 3992 with your buffer size value.

//ALLOCSPL JOB  (...),'SPOOL FORMAT',MSGLEVEL=1 
//FORMAT   EXEC PGM=IEBDG 
//*
//SPOOL    DD   DSN=SYS1.HASPACE,UNIT=3390,
//              VOL=SER=SPOOL2,DISP=(NEW,KEEP), 
//              SPACE=(CYL,884,CONTIG),
//              DCB=(DSORG=PSU,RECFM=U,BLKSIZE=3992)
//*
//SYSPRINT DD   SYSOUT=A 
//SYSIN    DD   * 
                DSD OUTPUT=(SPOOL) 
                FD NAME=SPOOL,FILL=X'FF',LENGTH=3992 
                CREATE NAME=(SPOOL),QUANTITY=99999999 
                END 
/*