Performance Tuning for Content Manager

Chapter 2. Content Manager base products 39

You can predict and control the size of this space by reviewing information about

database agents. Agents running on behalf of applications require substantial

memory space, especially if the value of MAXAGENTS is not appropriate.

For partitioned database systems, the fast communications manager (FCM)

requires substantial memory space, especially if the value of

FCM_NUM_BUFFERS is large. In addition, the FCM memory requirements are

either allocated from the FCM buffer pool, or from both the database manager

shared memory and the FCM buffer pool, depending on whether the partitioned

database system uses multiple logical nodes.

2.1.3 Performance-related concepts

The DB2 database management system provides a set of features and concepts

that are closely related to the performance of a DB2 database system. Some of

them reflect the architectural concepts that we discussed in 2.1.2, “DB2

architecture overview” on page 29. Depending on your specific database

application, each of them can cause a performance bottleneck in your database

environment if the database is not set up according to the requirements of the

application. Thus it is essential to know and understand these concepts for

effective DB2 performance tuning. In this section, we give an overview of these

concepts and describe how they affect database performance. In Chapter 8,

“Tuning DB2 for Content Manager” on page 171, we go through the individual

configuration steps to adjust the setup of your database environment. In 11.4,

“Monitoring and analysis tools for DB2” on page 295, we provide an overview of

the tools and techniques that enable you on the individual platforms to verify that

your current database setup meets your requirements.

This section requires you to be familiar with the basic concepts and architecture

as outlined in 2.1.1, “Basic DB2 database concepts” on page 20 and 2.1.2, “DB2

architecture overview” on page 29.

Among others, we specifically discuss the following performance-related

concepts:

 Query execution and access plan

 Indexes

 Data placement

 Clustering

Query execution and access plan

Any SQL query sent to the database is first passed to the SQL Compiler. As part

of this SQL Compiler process, the query optimizer analyzes a query. The

Compiler develops alternative strategies, called

access plans, for processing the

query. DB2 UDB evaluates the access plans primarily on the basis of information