Transaction recovery involves the transaction log file that is used as a write-ahead log, plus journal files maintained on a per-database basis. Log files contain short-term recovery information regarding active databases, while the journal files contain long-term information used for auditing and disaster recovery. While the log file is circular and wraps around, journal files are of configurable length and are retained indefinitely.

Actian X employs a page-oriented recovery scheme, where changes to pages are reflected in the transaction log file.

Recovery information is divided into two types:

Actian X performs both online and offline recovery, as described in Recovery Modes.

Undo or transaction backout recovery is performed by the DBMS Server. For example, when a transaction is aborted, transaction log file information is used to roll back all related updates. The DBMS Server writes the Compensation Log Records (CLRs) to record a history of the actions taken during undo operations.

A Redo recovery operation is database-oriented. Redo recovery is performed after a server or an installation fails. Its main purpose is to recover the contents of the DMF cached data pages that are lost when a fast-commit server fails. Redo recovery is performed by the recovery process. Redo recovery precedes undo recovery.

In an Actian X cluster environment where all nodes are active, the local recovery server performs transaction redo/undo for a failed DBMS server on its node, just like in the non-cluster case. The difference in a cluster installation is that if the recovery process (RCP) dies on one node, either because of an Actian X failure, or a general failure of the hardware, an RCP on another node will take responsibility for cleaning up transactions for the failed nodes.