Cancel Oracle Data Guard Managed Recovery

calendar Oct 25, 2025 / · 5 min read · oracle data guard database recovery standby database mrp sql commands database administration backup recovery V$MANAGED_STANDBY  ·
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How to Cancel Oracle Data Guard Managed Recovery

Overview

The ALTER DATABASE RECOVER MANAGED STANDBY DATABASE CANCEL command stops the Managed Recovery Process (MRP) on an Oracle Data Guard physical standby database. This command is essential when you need to perform maintenance operations, open the database in read-only mode, or troubleshoot synchronization issues between primary and standby databases.

SQL Code

1-- Cancel managed recovery
2ALTER DATABASE RECOVER MANAGED STANDBY DATABASE CANCEL;

Purpose

The cancel managed recovery command serves several critical purposes in Oracle Data Guard environments:

Primary Function: This command terminates the MRP process that continuously applies archived redo log files from the primary database to the standby database. The MRP process maintains transactional synchronization between databases, and stopping it allows administrators to perform specific operations that require the recovery process to be halted.

Common Use Cases: Database administrators use this command before opening a standby database in read-only mode, performing database shutdowns, converting to snapshot standby mode, or resolving synchronization gaps.

Code Breakdown

1ALTER DATABASE RECOVER MANAGED STANDBY DATABASE CANCEL;

Command Components

ALTER DATABASE: This is the main SQL statement that modifies database states and configurations.

RECOVER MANAGED STANDBY DATABASE: This clause specifies that the operation affects the managed recovery process on a physical standby database. The "managed" keyword indicates that Oracle automatically applies archived redo logs without manual intervention.

CANCEL: This keyword instructs Oracle to terminate the managed recovery process after applying the current archived redo file. The command provides session control back to the user once the recovery process completely terminates.

Key Points

Recovery Termination Timing: The CANCEL option terminates managed standby recovery after applying the current archived redo file. For faster termination, you can use CANCEL IMMEDIATE, which stops recovery after applying the current file or after the next redo log file read, whichever comes first.

Process Behavior: When executed, the command generates an ORA-16037 message in the alert log indicating "user requested cancel of managed recovery operation". The MRP0 background process shuts down, and the status changes to "Managed Standby Recovery Canceled".

Database State Requirements: The standby database must be in MOUNT state for this command to execute successfully. The database cannot be in NOMOUNT or OPEN READ WRITE mode when managing recovery operations.

Understanding the Command

When to Use This Command

Before Read-Only Access: You must cancel managed recovery before opening a standby database for read-only queries. After canceling recovery, execute ALTER DATABASE OPEN to enable read-only access.

During Maintenance Windows: Database administrators cancel managed recovery when performing incremental backups, refreshing standby databases, or resolving large synchronization gaps between primary and standby instances.

For Snapshot Standby Conversion: Before converting a physical standby database to snapshot standby mode, you must first cancel the managed recovery process. This allows the database to be opened in read-write mode for testing purposes.

Recovery Process Details

MRP Background Process: The Managed Recovery Process (MRP0) is the background process that reads redo data from standby redo logs or archived redo logs and applies changes to the standby database. This process consists of three phases: log read, redo apply, and checkpoint.

Verification After Cancellation: You can verify that MRP has stopped by querying the dynamic performance view: SELECT STATUS FROM V$MANAGED_STANDBY WHERE PROCESS='MRP0'. An empty result or "NOT RUNNING" status confirms successful cancellation.

Restarting Managed Recovery

Foreground Recovery: To restart recovery in the foreground after cancellation, use ALTER DATABASE RECOVER MANAGED STANDBY DATABASE. This keeps the session active until recovery is manually stopped.

Background Recovery: For background recovery that continues automatically, add the DISCONNECT FROM SESSION clause: ALTER DATABASE RECOVER MANAGED STANDBY DATABASE DISCONNECT FROM SESSION. This allows MRP to run independently without holding your session.

Best Practices

Proper Shutdown Sequence: Always cancel managed recovery before shutting down a standby database. Execute the cancel command first, then issue SHUTDOWN IMMEDIATE to ensure a clean database shutdown.

Monitoring During Cancellation: If the cancel command appears to hang, check the alert log for MRP process status and verify there are no blocking sessions. In some cases, you may need to use CANCEL IMMEDIATE NOWAIT for faster termination.

Gap Resolution: When large synchronization gaps exist between primary and standby databases, cancel recovery, take incremental backups from the standby's current SCN on the primary, and apply these backups before restarting managed recovery.

References

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