When a non-Oracle system is involved in a distributed transaction, the transaction capabilities of the non-Oracle system and the agent control whether it can participate in distributed transactions. Transaction capabilities are stored in the HS_CLASS_CAPS tables.
The ability of the non-Oracle system and agent to support two-phase commit protocols is specified by the 2PC type capability, which can specify one of the types shown in the following table.
| Type | Capability |
|---|---|
|
Read-Only (RO) |
The non-Oracle system can be queried only with SQL |
|
Single-Site (SS) |
The non-Oracle system can handle remote transactions but not distributed transactions. That is, it cannot participate in the two-phase commit protocol. |
|
Commit Confirm (CC) |
The non-Oracle system can participate in distributed transactions. It can participate in the server's two-phase commit protocol but only as the commit point site. That is, it cannot prepare data, but it can remember the outcome of a particular transaction if asked by the global coordinator. |
|
Two-Phase Commit (2PC) |
The non-Oracle system can participate in distributed transactions. It can participate in the server's two-phase commit protocol, as a regular two-phase commit node, but not as a commit point site. That is, it can prepare data, but it cannot remember the outcome of a particular transaction if asked to by the global coordinator. |
|
Two-Phase Commit Confirm (2PCC) |
The non-Oracle system can participate in distributed transactions. It can participate in the server's two-phase commit protocol as a regular two-phase commit node or as the commit point site. That is, it can prepare data and it can remember the outcome of a particular transaction if asked by the global coordinator. |
The transaction model supported by the driver and non-Oracle system can be queried from the HS_CLASS_CAPS Heterogeneous Services data dictionary view.
The following example shows one of the capabilities is of the 2PC type:
SELECT cap_description, translation FROM hs_class_caps WHERE cap_description LIKE '2PC%' AND fds_class_name LIKE 'SYBASE%'; CAP_DESCRIPTION TRANSLATION ---------------------------------------- ----------- 2PC type (RO-SS-CC-PREP/2P-2PCC) CC
When the non-Oracle system and agent support distributed transactions, the non-Oracle system is treated like any other Oracle server. When a failure occurs during the two-phase commit protocol, the transaction is recovered automatically. If the failure persists, the in-doubt transaction may need to be manually overridden by the database administrator.