Performance Tuning for Content Manager

Chapter 8. Tuning DB2 for Content Manager 251

Use the database system monitor to help tune this parameter in these ways:

 Calculating the peak number of transactions per second

Taking monitor samples throughout a typical day, you can determine your

transaction-intensive periods. Calculate the total transactions by adding the

following monitor elements:

– commit_sql_stmts (commit statements attempted)

– rollback_sql_stmts (rollback statements attempted)

Using this information and the available timestamps, you can calculate the

number of transactions per second:

MINCOMMIT = (commits + rollbacks) / 10

 Calculating the log space used per transaction

Using sampling techniques over a period of time and a number of

transactions, you can calculate an average of the log space used with the

following monitor element:

– log_space_used (unit of work log space used)

Changes to the value specified for this parameter take effect immediately; you do

not have to wait until all applications disconnect from the database.

8.6.39 Connection concentrator

Impact

DBM - Medium/High

Description

With connection concentrator, there is a shared pool of agent and stored

procedure processes for the Library Server database. Each connection uses

processes from the pool only during transactions. This enables many more client

connections to be processed efficiently. It also reduces memory use for each

connection and decreases the number of context switches. Connection

concentrator started with DB2 UDB V8.1.

All of the following parameters are database manager configuration parameters

of medium performance impact, with the exception of NUM_POOLAGENTS,

which has a high performance impact. Each of these parameters has been

discussed in detail in earlier sections of this chapter.

Note: The connection concentrator is enabled when the

MAX_CONNECTIONS database configuration parameter is set larger than

the MAX_COORDAGENTS configuration parameter.

252 Performance Tuning for Content Manager

How to view or set

You can enable and tune connection concentrator with the following parameters:

 MAX_CONNECTIONS

This parameter sets the largest number of allowed database connections.

This parameter should be larger than the total number of connections for the

mid-tier server plus the number of Windows client users. If you are using

mid-tier server connection pooling, then you can roughly calculate this

parameter as follows:

1/10 (# of Web users) + (# of Windows client users)

 MAXAGENTS

This parameter sets the largest number of database agents. At minimum, it

should be as high as the expected maximum number of concurrent

transactions in your system. If NUM_INITAGENTS (see next parameter) is set

very high, you might have to set this value even higher, in order to make room

for other kinds of agents. As a rough estimate, you can set it to:

1/10 (MAX_CONNECTIONS)

 NUM_INITAGENTS

This parameter sets the initial number of database agents. It should be set

somewhere around the expected or typical number of concurrent transactions

in your system.

 NUM_INITFENCED

This parameter sets the initial number of db2fmp “fenced” processes. Set this

to the same value as NUM_INITAGENTS.

 MAX_COORDAGENTS

This parameter sets the largest number of concurrent coordinating agents.

This number is usually set to the same as the number as MAXAGENTS.

 NUM_POOLAGENTS

This parameter sets the size of the agent pool. This number is usually set to

the same as the number of MAXAGENTS. When connection concentrator is

enabled, the number of agents specified here is only advisory. More agents

might be in the agent pool at any given time.

For example, consider a single database partition system in which, on average,

2,000 users are connected to the database. At times, the number of concurrent

transactions is as high as 100, but never higher than 200. Transactions are short.