zSeries File System
zFS is another type of OMVS file system that can be used which can be mounted into the
file system tree. zFS is not a replacement for HFS; in particular, the root file system
must be an HFS.
zFS Differences from HFS
- The zFS kernel runs in its own address space. HFS support is included in the OMVS
- The zFS is stored in a VSAM Linear Dataset. A special utility function is used to
format the zFS. When you mount a zFS, the file system type is specified as ZFS.
- Files which are approximately 8K or larger and are frequently accessed or files that
are accessed randomly may perform better in a zFS than an HFS.
- zFS data blocks are updated asynchronously. Changes to zFS metadata are logged so
that metadata updates can be automatically replayed in the event of a system failure.
- A zFS "aggregate" can hold more than one file system. In compatibility mode, a zFS
contains only one file system which has the same name as the zFS.
- The zfsadm command is used to manage the zFS. The zfsadm grow command can be
used to grow a zFS. A zFS can be configured to expand automatically once the existing space allocation
is used up; however, this is not the default.
- Data blocks can be shared between HFS files; very small files can be stored with the
directory information without using any data blocks.
Displaying zFS Information
The zfsadm lsfs command will display any active zFS:
IOEZ00129I Total of 1 file systems found for aggregate zfs.dataset.name
zfs.dataset.name RW (Mounted R/W) 1147 K alloc 1147 K quota On-line
Total file systems on-line 1; total off-line 0; total busy 0; total mounted 1
The zfsadm lsquota command displays space usage and quota for a zFS:
zfsadm lsq -f zfs.dataset.name
Filesys Name Quota Used Percent Used Aggregate
zfs.dataset.name 6335 1147 18 19 = 1292/6480 (zFS)
Quota refers to the current available space for a zFS file system.
Checking zFS Integrity
The IOEAGSLV program (the Salvager) can be used to verify zFS structural integrity. The
zFS must not be in use; otherwise you will receive a message like "unable to open dataset".
Refer to the publications below for parameter information.
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