Veritas Storage Foundation 5.1 SP1 Advanced Features Administrator"s Guide (5900-1503, April 2011)

Improving database

performance with Veritas

Concurrent I/O

This chapter includes the following topics:

■ About Concurrent I/O

■ Enabling and disabling Concurrent I/O

About Concurrent I/O

Veritas Concurrent I/O improves the performance of regular files on a VxFS file

system without the need for extending namespaces and presenting the files as

devices. This simplifies administrative tasks and allows databases, which do not

have a sequential read/write requirement, to access files concurrently. This chapter

describes how to use the Concurrent I/O feature.

Quick I/O is still an alternative solution for DMS tablespaces.

In some cases (for example, if the system has extra memory), Cached Quick I/O

may further enhance performance.

How Concurrent I/O works

Traditionally, UNIX semantics require that read and write operations on a file

occur in a serialized order. Because of this, a file system must enforce strict

ordering of overlapping read and write operations. However, databases do not

usually require this level of control and implement concurrency control internally,

without using a file system for order enforcement.

Chapter