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Administrator's Guide
Tivoli Storage Manager supports both journaled file system (JFS) files and
raw logical volumes as database, recovery log, and disk storage pool
volumes. JFS files have the following advantages:
- JFS locks open files, and other applications cannot write to them.
However, raw volumes are not locked, and any application can write to
them. Tivoli Storage Manager tries to prevent starting more than one
instance of the same server from the same directory, but it can be
done. If you are using raw volumes, both server instances can
simultaneously update the same information. This could cause errors in
the database, recovery log, or storage pool raw volumes.
- After a database, recovery log, or storage pool volume is defined, you
cannot change its size. Size information determines where data is
placed and whether volumes have been modified by other applications or
utilities. However, smit lets you increase the sizes of raw
volume. If the volume is defined before its size is increased, Tivoli
Storage Manager cannot use the volume or its data.
- For database and recovery log volumes you should use Tivoli Storage
Manager mirroring rather than AIX mirroring. If you use AIX mirroring
for database and recovery log volumes, you may have a problem with raw
volumes, but not with JFS files. AIX tracks mirroring activity by
writing control information to the first 512 bytes of USER area in a raw
volume. This is not a problem for database and recovery log volumes,
but Tivoli Storage Manager control information is also written in this
area. If AIX overwrites this control information when raw volumes are
mirrored, Tivoli Storage Manager may not be able to vary the volume
online.
- Note:
- Tivoli Storage Manager mirroring only supports database and recovery log
volumes. Disk storage pool volumes are not supported by Tivoli Storage
Manager mirroring.
The use of JFS files for database, recovery log, and storage pool volumes
requires slightly more CPU than is required for raw volumes. However,
JFS read-ahead caching improves performance.
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