SCF Reference Manual for the Storage Subsystem (G06.27+, H06.04+)

Storage Subsystem Commands
SCF Reference Manual for the Storage Subsystem—529937-008
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Disk Attribute Descriptions
unless you load the system from a saved system configuration database that
contains a smaller value for this attribute.
FORCED
specifies that the disk attribute values be changed without any interaction with the
user. SCF does not prompt for confirmation.
FSTCACHING { ON | OFF }
specifies that the free-space table (FST) for a disk is updated in memory (ON), that
the FST is updated on disk (OFF) or that DP2 decides whether to keep the FST in
memory or on disk (ENABLED). The default is OFF. FSTCACHING ON can
increase performance. The FST is always rebuilt from disk when the disk is
started.
The system disk always runs with FSTCACHING ON regardless of the configured
value.
FULLCHECKPOINTS { ENABLED | DISABLED | FORCED }
(nondirectory structured files only) specifies when to perform full-block
checkpoints.
For mirrored volumes, FULLCHECKPOINTS is important only if the primary or
mirror disk is not up. In that situation, FORCED or ENABLED can protect the
validity of data written to the disk.
When performing full-block checkpoints, the primary process checkpoints the data
to the backup process before writing to the disk. This action ensures that the data
on the disk is not corrupted even if a hardware freeze or processor halt occurs
during a disk write.
Use FORCED or ENABLED unless data loss is not critical.
HALTONERROR number
specifies whether an internally detected, unrecoverable, disk-process error forces
a halt (code %11500) in the primary processor, backup processor, or both. Forced
processor halts also halt the respective disk process. Forced processor halts can
provide more information at the time of a failure. To force a halt when a failure is
detected, set number to either 2, 3, or 4.
DISABLED Never use a full-block checkpoint to protect the data on the disk.
Using DISABLED maximizes disk performance, but risks
corrupting data blocks on the disk.
ENABLED Use a full-block checkpoint only when serial writes are not being
performed. Use ENABLED on disks that perform parallel writes
and on nonmirrored disks. For more details, see the
SERIALWRITES attribute on page 14-29. (Default)
FORCED Always use full-block checkpoint for disk-write operations.