Transaction recovery refers to the series of steps that the database performs in the event of a crash (either an instance crash or a transaction crash) to roll back uncommitted transactions.

Values:

• ENABLED - Transaction recovery is enabled for a PDB.

• DISABLED - Transaction recovery is disabled for a PDB.

During normal operation, the value of this parameter is set to ENABLED by the database and this setting should not be modified by a DBA. However, there are two circumstances under which it is permissible for a DBA to modify the value of this parameter:

• A quarantined transaction is a transaction that is isolated and for which transaction recovery will not be attempted while the quarantine on it remains. It requires intervention by the DBA to first resolve the issue that caused the transaction to be quarantined, and then to drop the transaction quarantine so that transaction recovery is attempted again. If transaction recovery becomes disabled on a PDB due to an excessive number of quarantined transactions (a process known as "transaction quarantine escalation"), then the database automatically sets the value of this parameter to DISABLED. When this happens, the DBA should take corrective action for the quarantined transactions, then restart transaction recovery for the PDB by setting the value of this parameter to ENABLED. Refer to Oracle Database Administrator’s Guide to learn about this entire process before you set this parameter.

• While working to resolve an issue, Oracle Support may instruct a DBA to temporarily disable transaction recovery by setting this parameter to DISABLED. After the issue has been resolved, this parameter should ultimately be set back to ENABLED so that normal database operation can resume.