IBM 000-8697 Manuale Utente

IBM Informix OnLine Database Server Administrator’s Guide

The

SPINCNT

 parameter affects only multiprocessor machines that use spin-

and-retry latch acquisition.

SPINCNT

 specifies the number of times that a

process attempts to acquire a latch in shared memory before it enters a wait
mode.

The default value of

SPINCNT

 on a uniprocessor machine is 0. The default

value of

SPINCNT

on a multiprocessor machine is 300. Refer to

for

information about tuning the value of this parameter.

This section explains how to allocate disk space for OnLine. The disk space
allocation task can be divided into four smaller tasks:

■

Decide whether to dedicate raw disk space or cooked files to OnLine

■

Determine how much disk space to dedicate to OnLine

■

Decide how to apportion the disk space (disk layout)

■

Allocate the disk space

This section describes the advantages and trade-offs between either
allocating raw disk space managed by OnLine or storing OnLine data in
cooked file space. As a general guideline, you experience greater perfor-
mance and increased reliability if you allocate raw disk space.

Each chunk (unit of disk space) that is dedicated to OnLine can be either one
of the following:

Cooked files are easier to allocate than raw disk space. However, you sacrifice
reliability and experience lower performance if you store OnLine data in
cooked files.

Raw disk space

I/O

 is managed by OnLine.

Cooked file

The file contents are managed by OnLine, but the

I/O

is managed by the

UNIX

 operating system.