IBM 000-8697 用户手册

Operating OnLine

Verify that the

DBSPACES

value in the configuration file will not be exceeded.

DBSPACES

 refer to the total number of blobspaces plus dbspaces.

When you create a blobspace, you specify the blobpage size as a multiple of
the machine-page size.

You specify an explicit pathname for the blobspace. Informix recommends
that you use a linked pathname. (Refer to

 for further information

about the benefits of using linked pathnames. Refer to

 for further

information about selecting a chunk pathname. Refer to

for guide-

lines on how to determine where your chunks should be located on disk.)

If you are allocating a raw disk device for the blobspace, you might need to
specify an offset to preserve track-0 information used by your

UNIX

operating system. (Refer to

determine if you need an offset.)

If you are allocating cooked disk space, the pathname is a file in a

UNIX

 file

system.

You can mirror the blobspace when you create it if mirroring is enabled for
OnLine. Mirroring takes effect immediately. (Refer to

information about the benefits of chunk mirroring.)

If you are logged in as user informix, you can create a blobspace from within

DB-M

onitor or from the command line. If you are logged in as root, you must

use the command-line option.

You can create a blobspace while OnLine is in online mode.

Blobpage size can vary among blobspaces. Blobpage size is a multiple of
OnLine page size (specified as

BUFFSIZE

 in the configuration file). You

specify blobpage size as some number of OnLine pages.

Aim to create a blobpage size that is the size of the most frequently occurring
blob. For example, if you are storing 160 blobs and you expect 120 blobs to be
12 KB and 40 blobs to be 16 KB, a 12-kilobyte blobpage size would store the
blobs most efficiently. If speed is your primary concern, use a 16-kilobyte
blobpage so that every blob can be stored on a single blobpage.