HP-UX Reference (11i v2 04/09) - 5 Miscellaneous Topics (vol 9)

s
st_ats_enabled(5) st_ats_enabled(5)
(Tunable Kernel Parameters)
NAME
st_ats_enabled - determines whether to reserve a tape device on open
VALUES
Failsafe
0 (off)
Default
1 (on)
Allowed values
0 (off) or any positive integer
(on)
Recommended values
0 (off) or 1 (on)
DESCRIPTION
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
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 other than ATS that this tunable
should be turned off. Most multi-node 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 multi-platform 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
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 parame-
ter 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.
Section 5−−334 Hewlett-Packard Company − 1 − HP-UX 11i Version 2: September 2004