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1-40 IBM Informix OnLine Database Server Administrator’s Guide
OnLine Disk Space Allocation
SPINCNT
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 page 5-24 for
information about tuning the value of this parameter.
OnLine Disk Space Allocation
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
Allocate Raw Disk Space or Cooked Files?
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 filesare 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.