1-24 IBM Informix OnLine Database Server Administrator’s Guide

Mirroring Configuration Guidelines

Mirroring Configuration Guidelines
Mirroringis not required, but it is strongly recommended. Refer to page 4-14
for a complete discussion of mirroring and mirroring administration.
Mirroringis a strategy that pairs primary chunks of one defined blobspace or
dbspace with equal-sized mirror chunks. Writes to the primary chunk are
duplicated asynchronously on the mirror chunk.
Any database that has extreme requirements for reliability in the face of
hardwarefailure should be located in a mirrored dbspace. Above all, the root
dbspace should be mirrored.
The same OnLine database server on the same host machine must manage
both chunks of a mirrored set. Mirroring on disks managed over a network
isnot supported. For a complete description of mirroring and how it works,
refer topage 4-14.

MIRROR

TheMIRROR parameter is a flag that indicates whether mirroring is enabled
for OnLine. The default value ofMIRROR is 0, indicating mirroring is
disabled. The alternative value of MIRROR is 1, indicating mirroring is
enabled.
Enablemirroring if you plan to create a mirror for the root dbspace as part of
initialization.Otherwise, leave mirroring disabled. If you later decide to add
mirroring, you can change the parameter value throughDB-Monitor or by
editing your configuration file. (Refer topage 3-104.)

MIRRORPATH

TheMIRRORPATH parameter specifies the full pathname of the chunk that
willserve as the mirror for the initial chunk of the root dbspace (ROOTPATH).
MIRRORPATH should be a link to the chunk pathname of the actual mirror
chunk for the same reasons thatROOTPATH is specified as a link. (Refer to
page 1-22.) Similarly, you should select a short pathname for the mirror
chunk.No default value is provided, but /dev/mirror_root is one suggestion
for a link pathname.