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3-114 IBM Informix OnLine Database Server Administrator’s Guide
Change the Maximum Number of Users
Change the Maximum Number of Users
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-Monitor; 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-Monitor or from the command line. If you are logged in as root, you must
use the command-line option.
From DB-Monitor
1. From within DB-Monitor, select the Parameters menu, Shared-
Memory option to change the maximum number of dbspaces.
Change the value in the field, Max # of Users.
2. Change the value of the LOCKS, BUFFERS, or TBLSPACES parameter
to match the new number of users, if required.
3. Reinitialize shared memory (take OnLine offline and then to
quiescent mode) for the change to take effect.