SCF Reference Manual for the Storage Subsystem (G06.24+, H06.03+)

Configuring Magnetic Disks
SCF Reference Manual for the Storage Subsystem—529937-007
6-23
Changing the Values of the Attributes for Magnetic
Disks
Changing the Values of the Attributes for Magnetic Disks
1. Display detailed information about the configured attributes of the disk you want to
alter:
-> INFO $DATA00, DETAIL
Displayed fields are defined starting on page 5-3. An asterisk (*) indicates the
attributes you can alter.
2. Change one or more Magnetic Disk Attributes (page 14-52). For example, this
command changes the revive attributes for the disk:
-> ALTER $DATA00, REVIVERATE 10, REVIVEPRIORITY 100
3. Verify the change is entered into the system configuration database:
-> INFO $DATA00, DETAIL
4. See Resetting a Magnetic Disk on page 7-11.
Configuring the Size of Disk Cache
The CACHE attribute (page 14-56) of the ALTER DISK command specifies the disk
cache configuration for an in-use volume.
Considerations for ALTER DISK, CACHE and Magnetic Disks
•
Using the ALTER DISK, CACHE command causes all disk caches to be flushed
when the cache configuration is changed.
•
A cache that is too large can degrade system performance, causing:
°
Excessive page faulting in the processor
°
A significant number of read faults on the cache
°
File-system errors indicating lack of memory (such as error 35 or 36)
°
Processor halts due to lack of memory (such as halt %11501)
•
Repeat this procedure as often as necessary to achieve:
°
Cache Read Hits: High
°
Cache Read Misses: Low
°
Cache Faults: Low
°
Audit Forces: Low
•
There can be up to eight disk processes for each volume. Each disk process in
the volume disk-process group requires a minimum configuration for each cache
Caution. Configuring the cache too small or too large can cause severe performance
problems.