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IBM Informix OnLine Database Server Administrator’s Guide

Users, in this context, refers to the maximum number of processes that attach
to shared memory. User processes include database server processes,
daemon processes, and utility processes. This value is specified as

USERS

 in

the configuration file.

You can make this change while OnLine is in online mode but the change
does not take effect until you reinitialize shared memory (take OnLine offline
and then to quiescent or online mode).

The maximum number of user processes that can concurrently attach to
shared memory is 1,000. The minimum value for

USERS

is the number of page

cleaners (specified as

CLEANERS

) plus 4, plus 1 if mirroring is enabled. The

four user processes that must be accommodated are tbinit, the master
daemon; tbundo, the undertaker daemon; tbmonitor, a utility process that
executes

DB-M

onitor; and one database server process to execute adminis-

trative tasks.

The minimum shared-memory values for

LOCKS

,

BUFFERS

, and

TBLSPACES

all depend on the value of

USERS

. Ensure that the change you make to the

value of

USER

 does not violate the minimum requirements for these three

values. If the value for

LOCKS

,

BUFFERS

, or

TBLSPACES

 is less than the

acceptable minimum, you must change it as well.

If you are logged in as user informix, you can make this change from within

DB-M

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

use the command-line option.

From within

DB-M

onitor, select the Parameters menu, Shared-

Memory option to change the maximum number of dbspaces.
Change the value in the field,

Max # of Users

.

Change the value of the

LOCKS

,

BUFFERS

, or

TBLSPACES

 parameter

to match the new number of users, if required.

Reinitialize shared memory (take OnLine offline and then to
quiescent mode) for the change to take effect.