Administration Guide

Other Configuration Considerations

You should consider the following configuration parameters when you are setting up your environment. For additional information about setting these parameters, refer to the DB2 Connect User's Guide.

Figure 41. Configuration Considerations

Database Manager Configuration Parameters

• tm_database

  This parameter identifies the name of the Transaction Manager (TM) database for each DB2 instance.

• spm_name

  This parameter identifies the name of the DB2 Connect sync point manager instance to the database manager. For resynchronization to be successful, the name must be unique across your network.

• resync_interval

  This parameter identifies the time interval (in seconds) after which the DB2 Transaction Manager, the DB2 server database manager, and the DB2 Connect sync point manager or the DB2 UDB sync point manager should retry the recovery of any outstanding indoubt transactions.

• spm_log_file_sz

  This parameter specifies the size (in 4 KB pages) of the SPM log file.

• spm_max_resync

  This parameter identifies the number of agents that can simultaneously perform resynchronization operations.

• spm_log_path

  This parameter identifies the log path for the SPM log files.

Database Configuration Parameters

• maxappls

  This parameter specifies the maximum permitted number of active applications. Its value must be equal to or greater than the sum of the connected applications, plus the number of these applications that may be concurrently in the process of completing a two-phase commit or rollback, plus the anticipated number of indoubt transactions that might exist at any one time. For more information about indoubt transactions, see Recovering from Problems During Two-Phase Commit.

• autorestart

  This database configuration parameter specifies whether the RESTART DATABASE routine will be invoked automatically when needed. The default value is YES (that is, enabled).

  A database containing indoubt transactions requires a restart database operation to start up. If autorestart is not enabled when the last connection to the database is dropped, the next connection will fail and require an explicit RESTART DATABASE invocation. This condition will exist until the indoubt transactions have been removed, either by the transaction manager's resynchronization operation, or through a heuristic operation initiated by the administrator. When the RESTART DATABASE command is issued, a message is returned if there are any indoubt transactions in the database. The administrator can then use the LIST INDOUBT TRANSACTIONS command and other command line processor commands to find get information about those indoubt transactions.

For more information about these configuration parameters, refer to the Administration Guide: Performance.

Host or AS/400 Applications Accessing a LAN Based DB2 Universal Database Server in a Multisite Update

DB2 Universal Database does not support multisite update from the host or AS/400 database clients using TCP/IP connectivity. In this situation, only SNA (Systems Network Architecture) connectivity is supported. The DB2 sync point manager is required for multisite update. DB2 Connect is not used in this scenario.

The database server that is being accessed from the host or the AS/400 database client does not have to be local to the workstation with the DB2 sync point manager. The host or AS/400 database client could connect to a DB2 UDB server using the DB2 sync point manager workstation as an interim gateway. This allows you to isolate the DB2 sync point manager workstation in a secure environment, while the actual DB2 UDB servers are remote in your organization. This also permits a DB2 common server Version 2 database to be involved in multisite updates originating from the host or AS/400 database clients.

The steps are as follows:

• On the workstation that will be directly accessed by the host or AS/400 application:
  1. Install DB2 Universal Database Enterprise Edition, or Enterprise - Extended Edition to provide multisite update support with the host or AS/400 database clients.
  2. Create a database instance on the same system. For example, you can use the default instance, DB2, or use the following command to create a new instance:

        db2icrt myinstance
     

  3. Supply licensing information, as required.
  4. Ensure that the registry value DB2COMM includes the value APPC.
  5. Configure SNA communications, as required. When the supported IBM SNA products are used, the SNA profiles required for the DB2 sync point manager are created automatically, based on the value of the spm_name database manager configuration parameter. Any other supported SNA stack will require manual configuration. For details, refer to the Installation and Configuration Supplement.
  6. Determine the value to be specified for the spm_name database manager configuration parameter. This parameter is pre-configured at DB2 instance creation time with a derivative of the TCP/IP host name for the machine. If this is acceptable and unique within your environment, do not change it.
  7. If necessary, update spm_name on the DB2 Universal Database server, using the UPDATE DATABASE MANAGER CONFIGURATION command.
  8. Configure communications required for this DB2 workstation to connect to remote DB2 UDB servers, if any.
  9. Configure communications required for remote DB2 UDB servers to connect to this DB2 server.
  10. Stop and restart the database manager on the DB2 Universal Database server to start the SPM for the first time.

      You should be able to connect to the remote DB2 UDB servers from this DB2 UDB workstation.

• On each remote DB2 UDB server that will be accessed by the host or AS/400 database client:
  1. Configure communications required for the remote DB2 UDB workstation with the DB2 sync point manager to connect to this DB2 UDB server.
  2. Stop and restart the database manager.