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Installation and Initial Configuration 1-33
Shared-Memory Parameter Guidelines
USERS
USERS specifies the maximum number of user processes that can concur-
rently attach to shared memory. The value can have a large effect on the size
of shared memory because it determines the minimum values for four other
shared-memory parameters (LOCKS, TBLSPACES, BUFFERS, and
TRANSACTIONS.)
To arrive at a value for
USERS, specify the highest likely value for the number
of user processes active at any one time plus the value of CLEANERS, plus 4.
Add one more user process if you intend to implement mirroring.
The minimum value is equal to the value of CLEANERS plus 4, plus 1 if
mirroring is enabled. The maximum value is 1000. The default value is 20.
(The four required user processes are the master daemon, tbinit; the under-
taker daemon, tbundo; the DB-Monitor process, tbmonitor; and one
additional user process to ensure a slot for an administrative process. If you
enable mirroring, an additional mirror daemon is needed.)
TRANSACTIONS
The value of TRANSACTIONS refers to the maximum number of concurrent
transactions supported by OnLine.
The minimum value of TRANSACTIONS is the value of USERS. The
maximum value is the number of transactions that can fit into a checkpoint
record, which for OnLine 5.x is 1,364.
By default, OnLine sets the value of TRANSACTIONS equal to the value of
USERS. DB-Monitor does not prompt for this value during initialization. The
default value is appropriate unless you plan to use OnLine in an X/Open
environment. If you are configuring OnLine for use with IBM Informix
TP/XA, refer to the IBM Informix TP/XA User Manual.
LOCKS
LOCKS specifies the maximum number of locks available to OnLine user
processes during processing. The number of locks has a relatively small effect
on the size of shared memory. The minimum value for LOCKS is equal to 20
locks per user process. The maximum value is 8 million. The default value is
2000.