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Tunable Kernel Parameters
HP-UX 11i Version 3: February 2007

Technical documentation

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st_ats_enabled — determines whether to reserve a tape device on open



0 (off)

Allowed values

0 (off) or 1 (on)

Recommended values

0 (off)


This tunable notifies the stape or estape driver whether it needs to reserve a tape device on open and subsequently release it on close. With this tunable on, the stape/estape driver will 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 others. DDS drives are not flagged for this functionality.

The st_ats_enabled tunable allows the safe sharing of tape devices in multinode 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/estape driver's open routine fails, a status of EBUSY is returned.

Who Is Expected to Change This Tunable?


Restrictions on Changing

Changes to this tunable take immediate effect and are used during the next open or close.

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/estape driver to use automatic reserve/release on open and close for multinode manageability.

What Are the Side Effects of Turning the Tunable On?

A reserve is sent to the tape device by the stape/estape 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 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/estape 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?



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.


st_ats_enabled was developed by HP.

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