DB2 registry file profile.reg usage

Content

It is not recommended to delete an instance entry from profiles.reg file.
The DB2 Instance Profile Registry file which stores the names of instances for the installed version of DB2 is named profiles.reg.

The file is located in the installation path under:

<installation path>/profiles.reg

Example:

/opt/ibm/db2/V9.5/profiles.reg

Performing a delete of instance entries from the profiles.reg file will cause your DB2 instance to start with default registry values. This is because when an instance is started, it looks in the profiles.reg first. If the instance name is missing, db2start doesn't know to read the instance registry variables defined in profiles.env. Thus db2start will load default values into the DB2 instance related registry variables, and then start the instance. The db2start command then will update and repair the profiles.reg file with the instance name if it was missing.

You can restart the instance to use the instance defined registry variables after the profiles.reg is repaired. Once restarted, the DB2 engine will pick up all the instance related registry variables defined in profiles.env file located under the instance directory sqllib.

An example of what could go wrong if you remove the instance name from profiles.reg, is when you start DB2 the first time it doesn't read DB2_NUM_CKPW_DAEMONS and the default value for that variable, which is 3, will be used if the release is DB2 V95, thus causing incorrect results if you had a different value for this parameter set at the instance level.