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Ask the Wizard Questions

BACKUP tuning

The Question is:

We have an Alpha 8400 with hsz40s and TZ88 tape drives.
We are backingup 20GB Raidsets to each tape drive. What
switches should we include in our Backup command to reduce
time to complete the backup? this will be an Oracle server.
It has 4GB of system memory.

The Answer is:

    Each switch that will reduce backup time will be because it reduces the
    backup error detection & recovery features.  The switches that
    fall into that category are: /NOCRC /GROUP=0 /NOVERIFY /BLOCK=65535

    Other things that might help during backup but make it much harder to
    restore is /PHYSICAL

    The most important thing in improving backup performance is actually
    process tuning.  See the VMS Version 5.2 New Features Manual,
    AA-LA97B-TE, page 2-15 through 2-17.  It has the best backup tuning
    hints ever published.  Beware that a well tuned BACKUP can saturate
    your I/O sub-system, and other users might be negatively impacted.
    It can also bring out hardware configuration glitches.

 UAF          Meaning                                Recommended
 Parameter                                             Value
 WSQUOTA      The number of pages of memory the      Equal to SYSGEN
              working set of the process can         parameter WSMAX

 WSEXTENT     The absolute limit of physical memory  Equal to
              allowed to the process.                WSQUOTA

              NOTE: BACKUP bases its memory
              consumption on the WSQUOTA
              value, not WSEXTENT.

 PGFLQUO      The number of pages of memory your     Greater than
              process is allowed in the page file.   or equal to
                                                     WSEXTENT up to

 FILLM        The number of files that can be open   Equal to
              simultaneously. BACKUP scans this      the SYSGEN
              number of files at one time.           parameter

 DIOLM        The number of direct I/O operations    Maximum of
              (usually disk operations) that can be  either (3 x
              outstanding simultaneously.            FILLM) or 4096

 ASTLM        The number of asynchronous system      Maximum of
              traps that can be queued to the        either (3 x
              process simultaneously.                FILLM) or 4096
						     Never lower than

 BIOLM        The maximum number of buffered I/O     Less than or
              operations that can be outstanding     equal to FILLM

 BYTLM        The total number of bytes of memory    Greater than
              that can be outstanding for buffered   or equal to
              I/O operations.                        the following
                                                     value: (256 x
                                                     FILLM) + (6 x

 ENQLM        The maximum number of locks that can   Greater than
              be queued simultaneously.              FILLM

 The following table lists a set of UAF parameter values that may be
 useful for your configuration:

      UAF Parameter  Value
      WSQUOTA        16,384
      WSEXTENT       Greater than or equal to WSQUOTA
      PGFLQUO        32,768
      FILLM             128
      DIOLM           4,096
      ASTLM           4,096
      BIOLM             128
      BYTLM          65,536
      ENQLM             256

 You can choose to set the values for WSQUOTA and FILLM lower than
 these values under the following circumstances:

      o  If your disks are highly fragmented, lower values prevent
         BACKUP from becoming highly CPU-intensive.

      o  If you use BACKUP during periods of heavy system use,
         lower values prevent BACKUP from consuming too many
         system resources.

 NOTE:   If you decrease the values of UAF parameters other than
         WSQUOTA and FILLM, use the ratios in the first table in
         this article to determine appropriate values.