You should consider the values of the following configuration parameters when you are setting up your environment. For additional information about setting these parameters, also refer to the DB2 Connect User's Guide.
Figure 39. Configuration Considerations
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The tm_database database manager configuration parameter identifies the name of the Transaction Manager (TM) database for each DB2 instance.
The spm_name database manager configuration parameter identifies the name of the DB2 Syncpoint Manager (SPM) instance to the database manager. It is defined in the system database directory and, if remote, in the node directory.
For resynchronization to be successful, the name must be unique across your network.
The resync_interval database manager configuration parameter identifies the time interval in seconds for which the DB2 Transaction Manager (TM) database manager, DB2 server database manger, and the DB2 Syncpoint Manager (SPM) should retry the recovery of any outstanding indoubt transactions.
The spm_log_file_sz database manager configuration parameter identifies the SPM log file size in 4K pages.
The spm_max_resync database manager configuration parameter identifies the number of agents that can simultaneously perform resync operations.
The spm_log_path database manager configuration parameter identifies the log path for the SPM log files.
The maxappls database configuration parameter specifies the maximum number of active applications allowed.
The value of this parameter must be equal to or greater than the sum of the connected applications plus the number of these same applications which may be concurrently in the process of completing a two-phase commit or rollback. This sum should then have added to it the anticipated number of indoubt transactions which might exist at any one time. See "Recovering from Problems During Two-Phase Commit" for more information on indoubt transactions.
As a result, if you have an environment like the one just described, you may need to increase the value of the maxappls parameter. Increasing the value helps ensure that all processes can be accommodated.
This database configuration parameter specifies whether the RESTART DATABASE routine will be invoked automatically when needed. The default is yes (that is, enabled).
A database containing indoubt transactions will require the RESTART DATABASE command/routine to be invoked in order to start up. If the autorestart option is not enabled, when the last connection to the database is dropped, the next connection will fail and require an explicit RESTART DATABASE again. This condition will exist until the indoubt transaction has been removed either by the transaction manager's resync operation, or through a heuristic operation performed by the administrator. When the RESTART DATABASE is issued, a message will be displayed if there are any indoubt transactions in the database. The administrator can then use the LIST INDOUBT TRANSACTION command and other command line processor commands to find out information about those indoubt transactions.
| Note: | Before installing either a fixpack for, or a new version of DB2, you should ensure that no indoubt transactions exist with any host or AS/400 server. Use the LIST DRDA INDOUBT TRANSACTION command to determine if any indoubt transactions exist. |