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1-24 IBM Informix OnLine Database Server Administrator’s Guide
Mirroring Configuration Guidelines
Mirroring Configuration Guidelines
Mirroring is not required, but it is strongly recommended. Refer to page 4-14
for a complete discussion of mirroring and mirroring administration.
Mirroring is 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
hardware failure 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
is not supported. For a complete description of mirroring and how it works,
refer to page 4-14.
MIRROR
The MIRROR parameter is a flag that indicates whether mirroring is enabled
for OnLine. The default value of MIRROR is 0, indicating mirroring is
disabled. The alternative value of MIRROR is 1, indicating mirroring is
enabled.
Enable mirroring 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 through DB-Monitor or by
editing your configuration file. (Refer to page 3-104.)
MIRRORPATH
The MIRRORPATH parameter specifies the full pathname of the chunk that
will serve 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 that ROOTPATH 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.