st_ats_enable.5 (2010 09)

s
st_ats_enable(5) st_ats_enable(5)
(Tunable Kernel Parameters)
NAME
st_ats_enable - determine whether to reserve a tape device on open
VALUES
Default
0 (off)
Allowed values
0 (off)
1 (on)
Recommended values
0 (off)
DESCRIPTION
Note: this tunable was named
st_ats_enabled
in releases prior to HP-UX 11i v3.
This tunable notifies the stape or estape driver whether it needs to reserve a tape device on open and sub-
sequently release it on close. When this tunable is on, the stape or estape driver will attempt to reserve
any tape device on open. The driver has a few tape devices flagged as suitable devices for this functional-
ity including: DLT 8000, DLT 7000, STK 9840, HP Ultrium, and others. DDS drives are not flagged for
this functionality.
The
st_ats_enable 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 or 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 effect immediately 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/ServiceGuard’s Advanced
Tape Sharing configuration or the user wants the stape or estape driver to use automatic reserve and
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 or estape driver on open and a release is sent on close.
No other initiator or HBA will be able to access the tape device while it is opened on another initiator or
HBA.
When Should the Tunable Be Turned Off?
This tunable should be turned off for any SAN tape sharing solution configuration other than ATS. Most
multinode backup applications (for example, Omniback) manage device reservation themselves, and any
interference by the stape or 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.
EXAMPLES
Query the current value of the tunable:
scsimgr get_attr -d estape
Set the value of the tunable to 1:
scsimgr set_attr -d estape -a st_ats_enable=1
HP-UX 11i Version 3: September 2010 − 1 − Hewlett-Packard Company 1