Veritas Storage Foundation™ for Oracle 5.0.1 Administrator's Guide

Using Veritas Cached Quick

I/O

This chapter includes the following topics:

■ About Cached Quick I/O

■ Enabling Cached Quick I/O on a file system

■ Determining candidates for Cached Quick I/O

■ Enabling and disabling Cached Quick I/O for individual files

About Cached Quick I/O

Veritas Cached Quick I/O maintains and extends the database performance benefits

of Veritas Quick I/O by making more efficient use of large, unused system memory

through a selective buffering mechanism. Cached Quick I/O also supports features

that support buffering behavior, such as file system read-ahead.

How Cached Quick I/O works

Cached Quick I/O is a specialized external caching mechanism specifically suitable

to 32-bit ports of the Oracle server. Cached Quick I/O can be used on 64-bit ports

of the Oracle server, but the benefits are not as great. Cached Quick I/O can be

selectively applied to datafiles that are suffering an undesirable amount of physical

disk I/O due to insufficient Oracle System Global Area (SGA). Cached Quick I/O

works by taking advantage of the available physical memory that is left over after

the operating system reserves the amount it needs and the Oracle SGA disk block

buffers cache has been sized to the maximum capacity allowed within a 32-bit

virtual address space. This extra memory serves as a cache to store file data,

effectively serving as a second-level cache backing the SGA.

Chapter