Veritas Storage Foundation for Oracle 5.0 Administrator's Guide, HP-UX 11i v3, Second Edition, December 2008

The second line of information is defined as follows:
■ CREAD is the number of reads from the VxFS cache (or total number of reads
to Quick I/O files with cache advisory on)
■ PREAD is the number of reads going to the disk for Quick I/O files with the cache
advisory on
■ HIT RATIO is displayed as a percentage and is the number of CREADS minus
the number of PREADS times 100 divided by the total number of CREADS. The
formula looks like this:
(CREADs - PREADs) * 100/ CREADs
The qiostat -l command output looks similar to the following:
OPERATIONS FILE BLOCKS AVG TIME(ms)
CACHE_STATISTICS
FILE NAME READ WRITE READ WRITE READ WRITE
CREAD PREAD HIT RATIO
/db01/cust.dbf 17128 9634 68509 38536 24.8 0.4
17124 15728 8.2
/db01/system.dbf 6 1 21 4 10.0 0.0
6 6 0.0
/db01/stk.dbf 62552 38498 250213 153992 21.9 0.4
62567 49060 21.6
OPERATIONS FILE BLOCKS AVG TIME(ms)
CACHE_STATISTICS
FILE NAME READ WRITE READ WRITE READ WRITE
CREAD PREAD HIT RATIO
OPERATIONS FILE BLOCKS AVG TIME(ms)
CACHE_STATISTICS
FILE NAME READ WRITE READ WRITE READ WRITE
CREAD PREAD HIT RATIO
Analyze the output to find out where the cache-hit ratio is above a given threshold.
A cache-hit ratio above 20 percent on a file for a given application may be sufficient
to justify caching on that file. For systems with larger loads, the acceptable ratio
may be 30 percent or above. Cache-hit-ratio thresholds vary according to the
database type and load.
109Using Veritas Cached Quick I/O
Determining candidates for Cached Quick I/O