This parameter identifies name of the Transaction Manager (TM) database for each DB2 instance. A TM database can be a local database or a remote database that is not accessed through DRDA protocols. The TM database is a database that is used as a logger and coordinator, and is used to perform recovery for indoubt transactions.
You may set this parameter to 1ST_CONN which will set the TM database to be the first database to which a user connects.
For more information about distributed unit of work, see the Administration Guide.
Recommendation: For simplified administration and operation you may wish to create a few databases over a number of instances and use these databases exclusively as TM databases.