Distributed transactions become in-doubt - Server machine running Oracle Database software crashes

Discussion

• Nirja Shah   -Posted on 22 Sep 15
  - The two-phase commit mechanism ensures that all nodes either commit or perform a rollback together.
  
  - What happens if any of the three phases fails because of a system or network error? The transaction becomes in-doubt.
  
  - Distributed transactions can become in-doubt in the following ways:
  1. A server machine running Oracle Database software crashes
  2. A network connection between two or more Oracle Databases involved in distributed processing is disconnected
  3. An unhandled software error occurs
  
  - The RECO process automatically resolves in-doubt transactions when the machine, network, or software problem is resolved.
  
  - Until RECO can resolve the transaction, the data is locked for both reads and writes.
  
  - The database blocks reads because it cannot determine which version of the data to display for a query.

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