NAME
st_ats_enabled — determines whether to reserve a tape device on open
VALUES
Allowed values
0 (off)
or
1 (on)
Recommended values
0 (off)
DESCRIPTION
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?
Anyone.
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?
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 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
st_ats_enabled
was developed by HP.
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