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   Using the BEA Tuxedo TOP END Domain Gateway

The TOP END Domain Gateway (TEDG) supports transactional message passing and queuing between BEA TOP END and BEA Tuxedo systems.

Specifically, the TEDG performs the following functions:

• Advertises the Transaction Manager Server (TMS) service and performs the associated transaction management functions currently performed by other Domains products

• Can act as a subordinate of transactions initiated by another client or server in the local domain

• Appears as the superior for transaction branches on remote nodes

• Can act as a subordinate for transactions coordinated by the BEA TOP END system. In this capacity the TEDG also serves as the coordinator for all server groups in the local domain.

Transaction Identifier Mapping

Both BEA TOP END and BEA Tuxedo systems follow the XA standard for transaction identifiers (XID). In the BEA Tuxedo system, the latter are referred to as Global Transaction Identifiers (GTRID). BEA TOP END users identify transactions with the term "XID." The XA XID is composed of a Global Transaction ID (GTRID) and a Branch Qualifier (BQUAL). The TEDG creates a new transaction branch for each new transaction step; this is known as a loosely-coupled relationship. Refer to Using GTRID Mapping in Transactions in Using the BEA Tuxedo Domains Component for details on loosely-coupled and tightly-coupled relationships. The TEDG supports loop-back transactions that span BEA TOP END or BEA Tuxedo systems multiple times. A new branch is generated for each hop.

For transaction branches destined for the BEA TOP END system, the TEDG creates a branch following the BEA TOP END branch design. For incoming transaction branches the BEA Tuxedo design is used.

The TEDG supports transaction management by providing transaction logging and recovery capabilities.

The TEDG logs the transaction state during the two-phase commit process to enable recovery. Each instance of the TEDG has its own log. The specification of the DMTLOG is given in the DM_LOCAL_DOMAINS section of the DMCONFIG file. As with other Domains features, the logging functionality is provided by the GWADM administrative server.

When a transaction has been committed on all nodes, the records for that transaction are removed from the log.

The TEDG performs recovery in a fashion identical to other Domains products.

When a domain gateway group is booted, the gateway performs an automatic warm start of the DMTLOG. The warm start includes a scan of the log to determine whether any transactions have not been completed. If incomplete transactions are found, action is taken to complete them.

• For a prepared transaction: The TEDG contacts the superior node for the transaction to determine whether the transaction should be committed or rolled back.

• For a committed transaction: The TEDG ensures that all subordinates have committed the transaction.

• Any transactions that are still in progress are rolled back.

The TEDG supports connections to BEA TOP END nodes that use the BEA TOP END Extended Recovery (XR) feature. The TEDG itself cannot be an XR node.

• How the TEDG Handles Connections and Message Passing

• Transactional Support Programming