Oracle Data Guard:switchover and failover Introduction

The role switching between Data guard master and subordinate libraries is divided into the following two kinds:

1) Switchover

Swithchover are usually artificial and planned for role swaps, such as upgrades. It is usually lossless, that is, there will be no loss of data. Its implementation is mainly divided into two stages:

Primary to standby.

Standby (one) to primary

2) Failover

Failover means that because primary failure cannot be recovered for a short time, standby has to act as a primay role, which is likely to result in data loss if in the highest performance mode.

The following shows the physical standby switchover and failover (logical standby switching is similar).

1. Physical Standby Execution switchover

1 Confirm whether Pirmary can be switched to standby

Primary>select switchover_status from V$database;

Switchover_status

--------------------

To STANDBY

2) switch primary to standby

Primary>alter database commit to switchover to physical standby;

3) Starting the original primary to Mount state

At this time the original primary is to standby identity in operation.

4 Confirm whether standby can be switched to primary

Standby>select switchover_status from V$database;

Switchover_status

--------------------

To PRIMARY

5) switch standby to Primary

Standby>alter database commit to switchover to primary;

Database altered.

Standby>alter database open;

Database altered.

6) Verify

Primary>select database_role from V$database;

Database_role