[Hadoop and Big data jobs]
[Hadoop and Big data jobs]
HFS and zFS are both used with Unix System Services but zFS is IBM’S preferred file system for Unix System Services files. From the Unix standpoint there’s no difference in HFS and zFS as far as mounting directories, the hierarchical structure, and accessing files or directories. The principal differences between the two are that zFS resides in a Virtual Storage Access Method (VSAM), linear, data set.

Each VSAM file can host several zFS file systems. zFS is basically a bit better than HFS as it is faster and uses space more efficiently and also supports files system based transaction logging for point in time recovery. The z/F S data and interfaces are DFS compliant.

ZFS files have DSORG=PO and DSTYPE=ZFS. There is another type of ZFS file called NFS, which allows you to access file spaces on remote servers.
Unlike HFS which runs in the USS address space, zFS runs in its own address space. zFS files need to be initialized before use whereas HFS files are ready to go once defined. However, zFS has performance limitiations for very large directories that are not seen with HFS. For exanple zFS is limited to 64K subdirectories per directory.

You use IDCAMS to allocate a ZFS datasets

DEFINE CLUSTER(NAME(zfs.file.name) –
CYLINDERS(prim sec) LINEAR SHR(2))

This is just a standard VSAM allocation, you make the file zFS by formatting it with the IOEAGFMT utility.
Note that the zfs file name in the format job is case sensitive and the parameters must be in lower case as shown.

//S1 EXEC PGM=IOEAGFMT,REGION=0M,
// PARM=(‘-aggregate zfs.file.name -compat’)
//SYSPRINT DD SYSOUT=*
//CEEDUMP DD SYSOUT=*
//STDERR DD SYSOUT=*
You can mount a ZFS file with the mount command

MOUNT FILESYSTEM(‘zfs.file.name’) MOUNTPOINT(‘path/name TYPE(ZFS) MODE(RDWR)’)

COPYTREE Command:

  1. Ensure both your SOURCE HFS and TARGET ZFS are mounted.
  2. Using TSO option 6, enter the following command :
    Copytree source target
    Your TSO session will be in locked out until the copy is complete.
    you also use the copytree command to copy data between two ZFS files
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