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

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st_fail_overruns(5) st_fail_overruns(5)
(Tunable Kernel Parameters)
NAME
st_fail_overruns - determines whether variable block mode read requests smaller than the physical record
size will fail
VALUES
Failsafe
0 (off)
Default
0 (off)
Allowed values
0 (off) or non-zero (on)
Recommended values
0 (off) or non-zero (on)
DESCRIPTION
This tunable determines whether variable block mode read requests through the stape driver, that are
smaller than the physical record size, will fail with the error [EFBIG].
For example, if a variable block mode read request of 32K was sent to a tape device with media of record
size 64K, the entire record’s data would not be returned to the host. If the tunable was set to
non-zero
(on), the read would be returned as failed with error [EFBIG]. If the tunable were set to
0 (off), the read
request would be returned as successful with a return value equal to the number of bytes read.
Who Is Expected to Change This Tunable?
Anyone.
Restrictions on Changing
Changes to this tunable take effect on the next boot.
When Should the Tunable Be Turned On?
If you want the stape driver to fail overrun variable block mode reads to tape as some applications
require.
What Are the Side Effects of Turning the Tunable On?
Variable block mode read requests through the stape driver that are smaller than the record fail with
[EFBIG].
When Should the Tunable Be Turned Off?
If you want the stape driver to handle an overrun read as a successful read, forcing you to retry the read
with the proper request size. This is the behavior most backup software expects.
What Are the Side Effects of Turning the Tunable Off?
The return value of the read must be checked to verify the number of bytes read equals the amount of
data requested on all variable block mode reads.
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.
AUTHOR
st_fail_overruns was developed by HP.
Section 5−−336 Hewlett-Packard Company − 1 − HP-UX 11i Version 2: September 2004