Distributed Transaction Management

Distributed Transaction Management within SAP ASE tracks the state of a transaction in the local SAP ASE/Component Integration Services, as well as in all remote servers participating in transactions.

When a user application commits a transaction, the commit is propagated to all participating remote servers using SAP ASE Transaction Coordinator (ASTC). The management of multisite transactions is handled by ASTC in cooperation with Component Integration Services. Component Integration Services registers new participating servers for each transaction, then turns over control of the transaction coordination to ASTC, which calls back into Component Integration Services to execute various commands for transaction management.

Internally, ASTC views a server as either:

These types map to the three sets of callbacks used, and map to server classes as indicated here:

• DTM-Enabled Servers
  Remote servers that are “DTM-enabled” support the full two-phase commit service enabled by ASTC.
• Pre-DTM servers
  Remote servers that are classified as “pre-DTM” are those that support transaction management statements such as begin tran, commit tran, rollback tran, but does not support one session’s ability to commit or rollback a transaction started by another session.
• strict DTM enforcement
  To ensure complete two-phase commit capability, ASTC uses the concept of strict dtm enforcement.
• Enable Component Integration Services
  ASTC relies on Component Integration Services to handle all communication with remote servers.
• Transactional RPCs
  The server allows RPCs to be included within the unit of work initiated by the current transaction.
• Restrictions on Transaction Management
  If nested begin transaction and commit transaction statements are included in a transaction that involves remote servers, only the outermost set of statements is processed.