Creating a ZFS – which way should I do it? IDCAMS LINEAR or IDCAMS ZFS?

When I looked into creating a ZFS (so I could run use it in the Unix environment) I found there were two ways of doing it both have the same end result.

The “old” way – a three step process

You use DEFINE CLUSTER …LINEAR to create the data set, then use PGM=IOEAGFMT to format it, then mount it.

//IBMUZFS  JOB ,' ',COND=(4,LE) RESTART=MOUNT 
//DEFINE   EXEC   PGM=IDCAMS 
//SYSPRINT DD     SYSOUT=* 
//SYSIN    DD     * 
  DELETE               COLIN.ZOPEN.ZFS   CLUSTER 
  SET MAXCC=0 
  DEFINE                - 
    CLUSTER             - 
    (NAME(COLIN.ZOPEN.ZFS)- 
    LINEAR              - 
    VOLUMES(USER10       )        - 
    STORCLAS(SGBASE ) - 
    MEGABYTES(6000 1000)  - 
    SHAREOPTIONS(3 3)) 
/*            - 
//FORMATFS EXEC   PGM=IOEAGFMT,REGION=0M,COND=(0,NE,DEFINE), 
// PARM=('-aggregate COLIN.ZOPEN.ZFS  ') 
//*  PARM=('-aggregate COLIN.ZOPEN.ZFS    -compat') 
//SYSPRINT DD     SYSOUT=* 
//STDOUT   DD     SYSOUT=* 
//STDERR   DD     SYSOUT=* 
//* 
//* 
//MOUNT    EXEC PGM=IKJEFT1A,COND=((0,NE,DEFINE),(0,NE,FORMATFS)) 
//SYSTSPRT DD   SYSOUT=* 
//SYSTSIN  DD   * 
    MOUNT FILESYSTEM('COLIN.ZOPEN.ZFS') TYPE(ZFS) + 
    MOUNTPOINT('/u/zopen') + 
    MODE(RDWR) PARM('AGGRGROW') AUTOMOVE 
/* 

The define took less than a second, the format took about 16 seconds, and the mount took less than one second

The Two step (sounds like a dance for system administrators)

You create the dataset with type ZFS, you then mount it, and the mount formats it.

//IBMUZFS  JOB ,' ',COND=(4,LE) RESTART=MOUNT 
//DEFINE   EXEC   PGM=IDCAMS 
//SYSPRINT DD     SYSOUT=* 
//SYSIN    DD     * 
  DELETE               COLIN.ZOPEN.ZFS   CLUSTER 
  SET MAXCC=0 
  DEFINE                - 
    CLUSTER             - 
    (NAME(COLIN.ZOPEN.ZFS)- 
    ZFS                 - 
    VOLUMES(USER10       )        - 
    STORCLAS(SGBASE ) - 
    MEGABYTES(6000 1000)  - 
    SHAREOPTIONS(3 3)) 
/* 
//MOUNT    EXEC PGM=IKJEFT1A,COND=((0,NE,DEFINE)) 
//SYSTSPRT DD   SYSOUT=* 
//SYSTSIN  DD   * 
    MOUNT FILESYSTEM('COLIN.ZOPEN.ZFS') TYPE(ZFS) + 
    MOUNTPOINT('/u/zopen') + 
    MODE(RDWR) PARM('AGGRGROW') AUTOMOVE 
/* 

The define took less than a second – the mount took 17 seconds, because it had to do the format.

What’s the difference?

Overall the time to execute the job was the same.

I think I prefer the first way of doing it, as I have more control, and can check the format was as I expected.

If you used the second way of doing it, defined the ZFS in parmlib, I don’t know if the formatting would hold up OMVS startup.

And don’t forget

And do not forget to update your parmlib member so the ZFS is mounted automatically at IPL.