It is strongly recommended that all DB2 specific registry values be defined in the DB2 profile registry. If DB2 variables are set outside of the registry, remote administration of those variables will not be possible, and the workstation will have to be rebooted in order for the variable values to take effect.
On OS/2, there are three system environment variables that are not stored in the DB2 profile registry: DB2INSTANCE, DB2PATH, and DB2INSTPROF. DB2INSTANCE and DB2PATH are set when DB2 is installed; DB2INSTPROF can be set after installation. The environment variable DB2PATH must be set; normally it is set during install and you should not modify it. Setting DB2INSTANCE and DB2INSTPROF is optional. Because the system environment variables are not set in the profile registry, you will need to reboot if you change their settings.
To change the setting of an environment variable, enter the following command:
set parameter=value
To determine the setting of an environment variable, enter:
echo %variable-name%
To modify system environment variables you must edit the config.sys file, then reboot to make the changes take effect.