Oracle Tips  by Burleson Consulting

The Data Warehouse Development Life Cycle

MANAGING A MULTITHREADED SERVER (MTS)

One of the problems faced by developers using SQL*Net version 1.0 was that each incoming transaction was spawned by the listener as a separate operating system task. With SQL*Net version 2.0, Oracle now has a method for allowing the listener connection to dispatch numerous sub-processes. With the MTS, all communications to a database are handled through a single dispatcher instead of separate Unix process IDs (PIDs) on each database. This translates into faster performance for most online tasks. Even local transactions will be directed through the MTS, and you will no longer see a PID for your local task when you issue ps -ef|grep oracle.

However, be aware that the MTS is not a panacea, especially at times when you want to invoke a dedicated process for your program. For Pro*C programs and I/O-intensive SQL*Forms applications--or any processes that have little idle time--you may derive better performance using a dedicated process.

In general, the MTS offers benefits such as reduced memory use, fewer processes per user, and automatic load balancing. However, it is often very confusing to tell whether the MTS is turned on--much less working properly.

Remember the following rules of thumb when initially starting the MTS:

* The MTS is governed by the init.ora parameters. If no MTS parms are present in init.ora, the MTS is disabled.

* The MTS is used when the MTS parms are in the init.ora and requests are made by service name (such as @myplace). In other words, you must retrieve the ROWID of all version 1.0 connect strings (such as t:unix1:myplace).

* Each user of the MTS requires 1 K of storage, so plan to increase your SHARED_POOL_SIZE.

* The V$QUEUE and V$DISPATCHER system tables indicate when the number of MTS dispatchers is too low. Even though the number of dispatchers is specified in the init.ora file, you can change it online in SQL*Remote DBA with the ALTER SYSTEM command, as follows:

SQLRemote DBA> ALTER SYSTEM SET MTS_DISPATCHERS = 'TCPIP,4';

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