12c, backup/recovery, RMAN

Oracle 12c – Detect and repair data failures with Data Recovery Advisor

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In Oracle 12c the Data Recovery Advisor is a part of Support Workbench which provides data corruption repair, database health checks, and RMAN functions.  It can perform the following:

  • Display data corruption problems.
  • Assess extent and impact.
  • Recommend repair options.
  • Automate repair processes.

Health checks are diagnostic procedures that assess the health of the database, they are executed reactively by an error occurring or manually.   The Data Recovery Advisor can diagnosis the following failures:

  • Datafiles or control files not accessible to database.
  • Physical corruption of datafiles.
  • Inconsistent datafile timestamps.
  • I/O failures such as hardware, OS drivers, exceeding OS resource limits.
  • Logical corruptions will require support interaction in general.

Failures are a persistent data corruption detected by a health check, normally found reactively when a problem is encountered and recorded in ADR.  The Data Recovery Advisor only after it occurs and assigns a priority of:

  • Critical – immediate action required to avoid database failure and corrupt.
  • High – importance may make some of database unavailable or corrupt.
  • Low – Failure can be ignored and will not cause database failure.

DRA Repairs are options which may include block media recovery, datafile media recovery, or Oracle Flashback Database.   DRA normally will provide both automated and manual recovery operations.   In automated repair DRA performance fix, verifies and clears error.

 

RMAN utility provides the ability to LIST, ADVISE and REPAIR failures.  RMAN is extracting this information from the ADR activities running in the database.  Commands used in RMAN for displaysing, advising, repairing, and changing failure check variables.

 

 

  • LIST FAILURE

 

RMAN> list failure;

using target database control file instead of recovery catalog

Database Role: PRIMARY

no failures found that match specification

RMAN>

 

  • ADVISE FAILURE – Displays repair options for failures.

 

RMAN> advise failure;

Database Role: PRIMARY

no failures found that match specification

RMAN>

 

  • REPAIR FAILURE – Allows you to repair failure with options, if there are automatic repairs from advise failure.

 

  • CHANGE FAILURE – allows you to set different priority to failure

 

RMAN> Change Failure 3 priority low;

 

 

Larry Catt

OCP

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