st_ats_enabled(5)                                         st_ats_enabled(5)
                          Tunable Kernel Parameters



 NAME    [Toc]    [Back]
      st_ats_enabled - determines whether to reserve a tape device on open

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

    Default    [Toc]    [Back]
      1 (on)

    Allowed values    [Toc]    [Back]
      0 (off) or any positive integer (on)

    Recommended values    [Toc]    [Back]
      0 (off) or 1 (on)

 DESCRIPTION    [Toc]    [Back]
      This tunable notifies the stape driver whether it needs to reserve a
      tape device on open and subsequently release it on close.  With this
      tunable on, the stape driver won't necessarily attempt to reserve any
      tape device on open.  The driver has a few tape devices flagged as
      suitable devices for this functionality.  This list includes the DLT
      8000, DLT 7000, STK 9840, HP Ultrium, and STK SD-3 drives.  DDS drives
      are not flagged for this functionality.

      The st_ats_enabled tunable allows the safe sharing of tape devices in
      multi-node configurations like MC/ServiceGuard's Advanced Tape
      Sharing.  The automatic reserve and release protects the tape device
      from being accessed from multiple nodes which would corrupt a backup.
      If the reserve portion of the stape driver's open routine fails, a
      status of [EBUSY] is returned.

    Who Is Expected to Change This Tunable?
      Anyone.

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

    When Should the Tunable Be Turned On?
      This tunable should be turned on if the system is going to be used in
      an MC/SG Advanced Tape Sharing configuration or the user wants the
      stape driver to use automatic reserve/release on open and close for
      multimode manageability.

    What Are the Side Effects of Turning the Tunable On?
      A reserve is sent to the tape device by the stape driver on open and a
      release is sent on close.  No other initiator/HBA will be able to
      access the tape device while it is opened on another initiator/HBA.

    When Should the Tunable Be Turned Off?
      It is recommended for any SAN tape sharing solution configuration



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






 st_ats_enabled(5)                                         st_ats_enabled(5)
                          Tunable Kernel Parameters



      other than ATS that this tunable should be turned off.  Most multinode
 backup applications like Omniback manage device reservation
      themselves and any interference by the stape driver may produce
      problems.  This tunable should also be turned off for any multiplatform
 SAN configuration to keep tape access across platforms more
      uniform.

    What Are the Side Effects of Turning the Tunable Off?
      Unauthorized access from another initiator might interfere with any
      current tape operation.

    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_ats_enabled was developed by HP.

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


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