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Lesson 3 Configuring the dispatchers for MTS, part 2
Objective Explain the function of mts_dispatchers.
The preceding lesson examined the first three init.ora dispatcher parameters required to initialize MTS. This lesson examines the critical mts_dispatchers parameter.
mts_dispatchers controls the number of dispatcher processes started at instance startup. You must estimate the number of dispatchers to start for each network protocol before instance startup. The optimal number of dispatcher processes for each instance depends upon:
  1. The performance you want from your database
  2. The host operating system's limit on the number of connections per process
  3. The number of connections required per network protocol
The instance must be able to provide as many connections as there are concurrent users on the database system. More dispatchers means users do not have to wait as long for dispatcher service.
Once you know the number of possible connections per process for your operating system, you can calculate the initial number of dispatcher processes per network protocol to create during instance startup, using the following formula:

number of dispatchers = maximum number of concurrent sessions

connections per dispatcher


For example, assume that your system typically has 80 users concurrently connected via TCP/IP and 40 users connected via SPX. In this case, the MTS_DISPATCHERS parameter should be set as follows:
MTS_DISPATCHERS = "(PROTOCOL=TCP) (DISPATCHERS=3)"
MTS_DISPATCHERS = "(PROTOCOL=SPX) (DISPATCHERS=3)"

Even though the number of dispatchers is specified in the init.ora file, you can change it online in Oracle’s Server Manager (SVRMGRL) with the ALTER SYSTEM command:
SRVMGRL> ALTER SYSTEM SET MTS_DISPATCHERS = 'TCPIP,4';
When several listeners are defined (or you are using SQL*Net 1.0 and 2.0), the user may connect to the server either via a dedicated server or via the MTS.
The next lesson examines the remaining three init.ora parameters required to initialize MTS.