Performance Tuning for Content Manager

Chapter 2. Content Manager base products 29

Most of the parameters affect either the amount of system resources that will be

allocated to a single instance of the database manager, or the setup of the

database manager and the different communications subsystems based on

environmental considerations. In addition, there are other parameters that serve

informative purposes only and cannot be changed. All of these parameters have

global applicability independent of any single database stored under that

instance of the database manager.

Database configuration file

A database configuration file is created when a database is created, and resides

where that database resides. There is one configuration file per database. Its

parameters specify the amount of resource to be allocated to that database.

Values for many of the parameters can be changed to improve performance or

increase capacity. Different changes might be required, depending on the type of

activity in a specific database.

Parameters for an individual database are stored in a binary configuration file

named SQLDBCON. This file is stored along with other control files for the

database in the SQLnnnnn directory, where nnnnn is a number assigned when

the database was created. Each database has its own configuration file, and

most of the parameters in the file specify the amount of resources allocated to

that database. The file also contains descriptive information, as well as flags that

indicate the status of the database.

In a partitioned database environment, a separate SQLDBCON file exists for

each database partition. The values in the SQLDBCON file might be the same or

different at each database partition, but we recommend that the database

configuration parameter values be the same on all partitions.

As we mentioned earlier, for a Content Manager system, we do not recommend

partitioning databases.

2.1.2 DB2 architecture overview

The previous section provides a brief overview of some of the basic relational

database concepts. Now we examine the DB2 architecture and processes as

shown in Figure 2-4 on page 30. Each client application, local or remote, is linked

with the DB2 client library. Local clients communicate using shared memory and

semaphores. Remote clients communicate using communication protocols such

as TCP/IP, Named pipes, NetBIOS, or IPX/SPX. Activities on DB2 server are

controlled by threads in a single process on Windows, or processes on UNIX.

They are denoted with circles or elliptical shapes. Those processes with thick

borders can be launched with multiple instances. For example, there might be

one or more subagents, loggers, prefetchers and page cleaners running, but

30 Performance Tuning for Content Manager

there is only one coordinator agent assigned for each client application. In the

following section, we go over the key DB2 components and processes.

Figure 2-4 DB2 architecture and processes overview

DB2 agents (coordinator agent and subagents)

DB2 agents

are the DB2 processes that carry out the bulk of SQL processing

requests from applications. They include coordinator agents and subagents. DB2

assigns a

coordinator agent for each client application. This agent coordinates

the communication and processing for this application.

If intra-partition parallelism is disabled (this is the default), then the coordinator

agent performs all of the application’s requests. If intra-partition parallelism is

enabled, then DB2 assigns a set of

subagents to the application to process

requests from the application. If the machine where the DB2 server resides has

multiple processors, multiple subagents can also be assigned to an application.

Database

Log buffer

Common

prefetch

request

queue

Logical

agents

Client

application

Client

application

Write log

request

Shared memory and semaphores,

TCPIP, Named pipes, NetBIOS,

SNA, IPX/SPX

Coordinator

agent

Coordinator

agent

Subagents Subagents

Async I/O

prefetch

requests

Scatter/Gather

I/Os

UDB Client Library

Clients

Page cleaners

Deadlock

detector

Logger

Log

Hard disksHard drive Hard disksHard disks

Prefetchers

Parallel, big-block,

read requests

Buffer

Pool(s)