This article describes about the Oracle 19C new feature – Active Data Guard DML Redirection.

ACTIVE DATA GUARD DML REDIRECT feature enables DML operation on the standby database to be redirected to and run on the primary database instead of failing, where the data changes will be applied. The updated data will then be streamed back to the standby database to maintain redundancy.

As the operations actually perform on primary, so better to avoid running too many DMLs on Active Data Guard standby databases.It might impact the performance of the primary due to too many DML operations.But it is good for applications that mostly read-applications with rare DML executions.

Below steps to achieve Applying DML on standby database:

  • User executes DML against open standby database.
  • DML redirects to the primary database.
  • Then DML is applied to the primary database.
  • Then the data change is streamed back to the standby database.
  • Data is visible to the client.

DML REDIRECT can be configured at the the system level or the session level by set the parameter ADG_REDIRECT_DML using below commands.The session level setting overrides the system level setting.

Enable ADG_REDIRECT_DML at System Level:

alter system set ADG_REDIRECT_DML=TRUE scope=both;

Enable ADG_REDIRECT_DML at Session Level:

alter session enable adg_redirect_dml;

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