Enhance performance using the connection concentrator in the DB2 Universal Database V8

Brief introduction

A connection concentrator is a new feature in the IBM DB2 Universal Database Version 8.0 (DB2 UDB) that handles a large number of inbound connections that have very short transactions but have relatively large delays. This feature has the following advantages:

system resources are not occupied by connections that do not perform any work (idle connections).

Because of multiplexing architectures, agents can switch from one to the other to serve many client applications.

The server resource limit is based on the actual transaction load, not on the number of connections.

For example, suppose you have a WEB application in which users connect to a database rather than perform a large number of transactions on a table record. The connection concentrator allows the user to appear to be connected to the database, while the actual database agent can still serve inbound requests.

Here are some scalability and performance enhancements:

Less system resources are required than other systems running the same load.

Control structures are divided into application-level and proxy-level data.

Each connection requires less memory (on average) and fewer processes.

Enable Connect Concentrator

Set the following parameters in the Database Manager configuration to enable the connection concentrator:

The value of the max_connections must be greater than the value of max_coordagents to open the connection concentrator.

By default, the max_connections parameter equals max_coordagents, so the connection concentrator is not enabled. This parameter controls the maximum number of applications that are allowed to connect to an instance. The range is [-1; max_coordagents--64000].

The max_coordagents parameter is the maximum number of coordination agents that can exist in the instance. Each local or remote application transaction is serviced by a coordinating agent.

When a connection concentrator is enabled, Max_connections restricts the number of user connections, max_coordagents the number of agents that are serving transactions.

The working principle of the connecting concentrator

DB2 UDB uses a database agent to service connection requests. Each user connection assigns a database agent. The agent exists throughout the life cycle of the connection, regardless of the workload running on the connection. Once the connection concentrator is enabled, the database agent is only "hot" during the SQL transaction. At the end of the transaction boundary (commit or rollback), the database agent is detached from the application. The agent is then free and can serve other transaction requests from other applications.

Figure 1. Connecting Concentrator Architecture