The number of connections required by the broker to its database depend to some extent on the actions of the message flows it is processing. The following connections are required for each broker:
On Windows, UNIX, and Linux, to avoid breaking global coordination, database connections are released only for message flows that are not globally coordinated.
Additionally on z/OS,
database connections for globally coordinated message flows are
released if the database has not been accessed for one minute.
If you are using the same database for several brokers, you must take account of all brokers in your calculations.
The connections for neighbors and publication nodes are required only if you are using retained publications.
When you start a broker, it opens all connections that it requires to the broker database for its own operation. When you stop the broker, it releases all current database connection handles.
If you are using DB2 for your database, the default action taken by DB2 is to limit the number of concurrent connections to a database to the value of the maxappls configuration parameter. The default for maxappls is 40. If you believe the connections that the broker might require exceeds the value for maxappls, increase this and the associated parameter maxagents to new values based on your calculations.
On all platforms except HP-UX (Integrity platform), parts of the broker need 32-bit access to the data source. You must therefore always define a 32-bit ODBC data source name (DSN) for the broker to connect to the broker database; this is true even if the broker has a 64-bit database, in which case you must present the broker with an environment that provides a 32 bit-compatible interface to the database (see Setting your environment to access databases). On HP-UX (Integrity platform) the broker is a 64-bit application so you must always define a 64-bit ODBC DSN for the broker to connect to the broker database.
The execution group on a broker must be able to connect to the broker database too. A 32-bit execution group on a 32-bit broker can connect to the broker database using the same 32-bit DSN definition that the broker uses. A 64-bit execution group on a 32-bit broker, however, needs a 64-bit ODBC connection to be able to connect to the broker database, so you must define a 64-bit ODBC DSN for the broker database in addition to the broker's 32-bit DSN definition.
When message flow transactions are globally coordinated, the queue manager must also be able to connect to the broker database; if the transactions are globally coordinated by a 64-bit queue manager (all WebSphere MQ Version 6 queue managers on 64-bit platforms are 64-bit), you must define a 64-bit ODBC DSN for the broker database, even if the broker and the execution group are 32-bit applications.
On HP-UX (Integrity platform), the 64-bit broker can have only 64-bit execution groups so the execution group can access the broker database using the same 64-bit DSN definition that the broker uses; a 32-bit DSN definition is not required.
For 32-bit and 64-bit considerations when connecting to user databases, see User database connections.
For help when you are deciding whether to create 32-bit DSNs, 64-bit DSNs, or both for your broker database, see Enabling connections to the databases.