MySQL server options can either be given as a parameter to mysqld, or it can be 

written in the MySQL option files. The options are read from different files in the 

order of preference as shown in Table 8 1.

Table 8 1   MySQL options files

Preference

Filename

Purpose

1

/etc/my.cfg

Global options

2

DataDir/my.cfg

Server specific options

3

defaults extra file

The file specified with 

  defaults extra file=path 

4

~/.my.cnf 

User  specific options

Another way to tune MySQL is by running 

mysqld

 with 

  name=value

 to set the 

variable. 

You can also set MySQL database variables using the 

SET

 command when your 

server is running. It can be executed with two modes:

Global

This mode sets options at the server level; if a new connection is created

the 

new values are used:

mysql>SET GLOBAL sort_buffer_size=1000000;

Session

In this mode, the option you set will remain valid until the current session 

ends, or until you set the option to different values. It can be used as the 

following:

mysql>SET SESSION sort_buffer_size=1000000;

8.6.2  DB2 UDB configuration

DB2 UDB has two levels of configuration:

DB2 profile registry

DB2 profile registry variables control the DB2 environment. Information stored in 

these profile registries are used by the DB2 server instance, and the DB2 

applications started after the changes are made. DB2 UDB provides the 

following different levels of profile registry:

The DB2 Instance Level Profile Registry

The DB2 Global Level Profile Registry

The DB2 Instance Node Level Profile Registry

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MySQL to DB2 UDB Conversion Guide