A Linux® instance can encounter
DASDs that are locked by another system.
Such a DASD is
referred to as
externally locked
or
boxed
. The
Linux instance cannot analyze
a DASD while it is externally locked.
About this task
To check whether a DASD has been externally locked, read its availability attribute. This
attribute should be good
. If it is boxed
, the DASD has been externally locked.
Because a boxed DASD might not be recognized as DASD, it might not show up in the device driver
view in sysfs. If necessary, use the device category view instead.
CAUTION:
Breaking an external lock can have unpredictable effects
on the system that holds the lock.
Procedure
- Optional: To read the availability
attribute of a DASD, issue a command of this form:
# cat /sys/bus/ccw/devices/<device_bus_id>/availability
Example: This example shows that a DASD with device bus-ID 0.0.b110
(device number 0xb110) has been externally
locked.
# cat /sys/bus/ccw/devices/0.0.b110/availability
boxed
If the DASD is an ECKD type
DASD and if you know the device bus-ID, you can break the external
lock and set the device online. This means that the lock of the external
system is broken with the
unconditional reserve
channel command.
-
To force a boxed DASD online, write
force to the online device attribute.
Issue a command of this form:
# echo force > /sys/bus/ccw/devices/<device_bus_id>/online
Example: To force a DASD with device number 0xb110 online issue:
# echo force > /sys/bus/ccw/devices/0.0.b110/online
Results
If the external lock is successfully broken or
if the lock has been surrendered by the time the command is processed,
the device is analyzed and set online. If it is not possible to break
the external lock (for example, because of a timeout, or because it
is an FBA-type DASD), the device remains in the boxed state. This
command might take some time to complete.For information about
breaking the lock of a DASD that has already been analyzed see tunedasd - Adjust low-level DASD settings.