Veritas Storage Foundation 5.1 SP1: Storage and Availability Management for Oracle (5900-1504, April 2011)

-rw-r--r-- 1 oracle10g dba 186 May 3 15:03 PROD.ora
./EMP_INDEX:
total 204808
-rw-r--r-- 1 oracle10g dba 104861696 May 3 15:43
ora_emp_inde_BEakGfun.dbf
./EMP_TABLE:
total 204808
-rw-r--r-- 1 oracle10g dba 104861696 May 3 15:43
ora_emp_tabl_BEak1LqK.dbf
About Cached ODM
ODM I/O normally bypasses the file system cache and directly reads from and
writes to disk. Cached ODM enables some I/O to use caching and read ahead, which
can improve ODM I/O performance. Cached ODM performs a conditional form of
caching that is based on per-I/O hints from Oracle. The hints indicate what Oracle
will do with the data. ODM uses these hints to perform caching and read ahead
for some reads, but ODM avoids caching other reads, even for the same file.
Considerations for using Cached ODM
Cached ODM is most useful for read-intensive workloads. For write-intensive
workloads or low memory environments, Cached ODM is not advised.
Cached ODM advantages over ODM:
■ ODM does direct I/O
■ Oracle can use larger System Global Area (SGA).
■ Read-aheads are not supported.
■ Some read-intensive Oracle workloads can perform poorly when ODM is used.
■ Oracle SGA is not good enough for some cases where a host may have more
than one database.
■ Host may have more than one database. (Pagecache can serve multiple
databases.)
■ Parallel Query processes many times do not use SGA
See “Enabling Cached ODM for file systems” on page 76.
63Overview of database accelerators
About Cached ODM