st_fail_overruns(5)                                     st_fail_overruns(5)
                          Tunable Kernel Parameters



 NAME    [Toc]    [Back]
      st_fail_overruns - determines whether variable block mode read
      requests smaller than the physical record size will fail

 VALUES    [Toc]    [Back]
    Failsafe
      0 (off)

    Default    [Toc]    [Back]
      0 (off)

    Allowed values    [Toc]    [Back]
      0 (off) or non-zero (on)

    Recommended values    [Toc]    [Back]
      0 (off) or non-zero (on)

 DESCRIPTION    [Toc]    [Back]
      This tunable determines whether variable block mode read requests
      through the stape driver, that are smaller than the physical record
      size, will fail with the error [EFBIG].

      For example, if a variable block mode read request of 32K was sent to
      a tape device with media of record size 64K, the entire record's data
      would not be returned to the host.  If the tunable was set to non-zero
      (on), the read would be returned as failed with error [EFBIG].  If the
      tunable were set to 0 (off), the read request would be returned as
      successful with a return value equal to the number of bytes read.

    Who Is Expected to Change This Tunable?
      Anyone.

    Restrictions on Changing    [Toc]    [Back]
      Changes to this tunable take effect on the next boot.

    When Should the Tunable Be Turned On?
      If you want the stape driver to fail overrun variable block mode reads
      to tape as some applications require.

    What Are the Side Effects of Turning the Tunable On?
      Variable block mode read requests through the stape driver that are
      smaller than the record fail with [EFBIG].

    When Should the Tunable Be Turned Off?
      If you want the stape driver to handle an overrun read as a successful
      read, forcing you to retry the read with the proper request size.
      This is the behavior most backup software expects.

    What Are the Side Effects of Turning the Tunable Off?
      The return value of the read must be checked to verify the number of
      bytes read equals the amount of data requested on all variable block



 Hewlett-Packard Company            - 1 -      HP-UX 11i Version 2: Sep 2004






 st_fail_overruns(5)                                     st_fail_overruns(5)
                          Tunable Kernel Parameters



      mode reads.

    What Other Tunables Should Be Changed at the Same Time?
      None.

 WARNINGS    [Toc]    [Back]
      All HP-UX kernel tunable parameters are release specific.  This
      parameter may be removed or have its meaning changed in future
      releases of HP-UX.

      Installation of optional kernel software, from HP or other vendors,
      may cause changes to tunable parameter values.  After installation,
      some tunable parameters may no longer be at the default or recommended
      values.  For information about the effects of installation on tunable
      values, consult the documentation for the kernel software being
      installed. For information about optional kernel software that was
      factory installed on your system, see HP-UX Release Notes at
      http://docs.hp.com.

 AUTHOR    [Toc]    [Back]
      st_fail_overruns was developed by HP.

 SEE ALSO    [Toc]    [Back]
      scsi_tape(7).


 Hewlett-Packard Company            - 2 -      HP-UX 11i Version 2: Sep 2004