Oracle Dataguard - Apps DBA Diaries

Oracle Data Guard Protection Modes: A Simple Guide

Oracle Data Guard is a crucial feature in Oracle Database that ensures high availability, data protection, and disaster recovery. It helps businesses maintain continuous access to their databases by keeping standby copies in sync with the primary database. One of the most important aspects of Oracle Data Guard is its protection modes, which determine how the data is protected in a disaster recovery scenario.

In this blog post, we’ll explain the three Oracle Data Guard protection modes in simple terms so you can choose the best one for your organization. Plus, we’ll focus on high CPC (cost-per-click) keywords related to database high availability and disaster recovery, which are essential for businesses relying on Oracle databases.

What are Oracle Data Guard Protection Modes?

Oracle Data Guard provides three main protection modes to manage how your database is protected and how quickly changes are applied to the standby databases. These modes are:

Maximum Protection Mode
Maximum Availability Mode
Maximum Performance Mode

Let’s dive into each one!

1. Maximum Protection Mode

Maximum Protection Mode is the highest level of data protection offered by Oracle Data Guard. In this mode, Oracle guarantees that no data will be lost in case of a failure. Here’s how it works:

Synchronous Redo Transport: Data changes are written to the primary database and then sent to the standby database immediately.
Zero Data Loss: If the primary database fails, the system ensures that no committed transactions are lost. The failover process is automatic, meaning you won’t lose any data.
Performance Impact: Because data changes need to be transmitted to the standby database before they are committed, it can impact the performance of the primary database.

When to use Maximum Protection Mode:

For businesses that require zero data loss, such as financial institutions or healthcare systems that need to maintain high data integrity.
When your organization cannot afford any downtime or loss of data due to system failures.

2. Maximum Availability Mode

Maximum Availability Mode offers a balanced approach between data protection and database performance. It provides high availability while minimizing the risk of data loss:

Synchronous Redo Transport: Like Maximum Protection Mode, data is sent to the standby database synchronously.
Data Loss Prevention: However, if the primary database or the primary site fails, Oracle can switch to the standby database without data loss, provided the standby is available.
Performance Consideration: This mode is designed to provide high availability without significantly impacting performance. If the standby database is not reachable for any reason, Oracle will automatically switch to Maximum Performance Mode to avoid application downtime.

When to use Maximum Availability Mode:

Ideal for organizations where minimizing downtime is more important than ensuring zero data loss, such as in e-commerce or online services.
When your system can tolerate occasional data loss if there’s a significant impact on performance or availability.

3. Maximum Performance Mode

Maximum Performance Mode is the default and most commonly used protection mode in Oracle Data Guard. It is designed for businesses that prioritize performance over data protection. Here’s how it works:

Asynchronous Redo Transport: In this mode, data changes are written to the primary database and then sent to the standby database asynchronously. This means the primary database does not wait for the standby database to confirm receipt of the changes before continuing with transactions.
No Guarantee of Zero Data Loss: Because data changes are not immediately applied to the standby database, there is a possibility of data loss if the primary database fails before the changes are propagated.
Performance Benefit: The primary benefit is performance. Since the primary database is not waiting for the standby database, it can handle transactions much faster and with minimal impact.

When to use Maximum Performance Mode:

For businesses where performance is the top priority, such as high-transaction environments like retail or online banking.
When you can afford to lose a small amount of data if the primary system fails unexpectedly.

Choosing the Right Protection Mode for Your Business

The right protection mode for your Oracle Data Guard setup depends on your specific business needs and the level of protection required. Here are some things to consider:

Data Sensitivity: If your business cannot afford to lose any data (e.g., in the healthcare or finance sector), Maximum Protection Mode is your best choice.
Availability vs. Performance: If your main concern is maintaining high availability with minimal performance impact, Maximum Availability Mode is a great balance.
Performance Priority: If your priority is fast transaction processing and your business can tolerate occasional data loss, Maximum Performance Mode will give you the best performance.

Oracle Data Guard is a powerful tool for ensuring high availability and disaster recovery. Understanding the different protection modes (Maximum Protection, Maximum Availability, and Maximum Performance) is crucial in choosing the right configuration for your business.

For organizations where data loss prevention is crucial, Maximum Protection Mode provides the highest level of security. However, if you prioritize both availability and performance, Maximum Availability Mode may be the right fit. For those where performance is paramount, Maximum Performance Mode offers the best speed with minimal data protection.

As you continue to plan your disaster recovery and data protection strategies, Oracle Data Guard protection modes are a key component in ensuring that your critical business data is secure and always available.

What is the difference between Switchover and Failover in Oracle Dataguard?

A switchover means just switching roles between the primary database and standby db.
nswitchover, the primary database chnaged to a standby role, and the standby database changed to the primary role.
This is typically done for planned maintenance of the primary db server.

A failover is when the primary database fails and one of the standby databases is
transitioned to take over the primary role. Failover is performed only in the event
of a catastrophic failure of the primary database, and there is no possibility of
recovering the primary database in a timely manner. Failover may or may not result
in data loss depending on the protection mode in effect at the time of the failover.

How to check if MRP Process is Running

Below Query is Used to verify if MRP process is running fine on Standby Database, after any maintenance activity that requires disconnect to Primary and Standby database.

SQL> SELECT CLIENT_PROCESS, PROCESS, THREAD#, SEQUENCE#, STATUS FROM V$MANAGED_STANDBY;

Below is the sample output from the query:

SQL> SELECT CLIENT_PROCESS, PROCESS, THREAD#, SEQUENCE#, STATUS FROM V$MANAGED_STANDBY;

CLIENT_P PROCESS THREAD# SEQUENCE# STATUS

——– ——— ———- ———- ————

ARCH ARCH 2 101072 CLOSING

ARCH ARCH 0 0 CONNECTED

ARCH ARCH 1 298101 CLOSING

ARCH ARCH 2 103073 CLOSING

ARCH ARCH 3 95398 CLOSING

ARCH ARCH 1 296100 CLOSING

ARCH ARCH 3 95399 CLOSING

ARCH ARCH 3 95400 CLOSING

ARCH RFS 0 0 IDLE

LGWR RFS 2 101074 IDLE

LGWR RFS 1 296102 RECEIVING

UNKNOWN RFS 0 0 IDLE

LGWR RFS 3 95401 IDLE

UNKNOWN RFS 0 0 IDLE

17 rows selected.

Convert Physical database into a Snapshot Standby Database

What are the benefits of Snapshot standby database?

Snapshot Standby Database is introduced from Oracle 11gR1. A Snapshot Standby database is a physical standby that is temporarily disconnected from Data Guard configuration, and started in READ-WRITE mode.It functions as a updateable Stand-alone Database, which is an exact Replica of Primary Database which is normally used for testing purpose. We can revert the Snapshot standby database to Physical Standby database after the testing is completed.

Steps to convert Physical database into a Snapshot Standby Database:

1. First step to convert to Snapshot standby database is to enable FLASHBACK feature on the Physical Standby, if not already enabled.

Ensure there is sufficient space available in Flash Recovery Area (FRA) for Flashback Logs.

2. Stop redo apply on the physical standby database:

SQL>alter database recover managed standby database cancel;

3. Turn on flashback logging:

SQL>alter database flashback on;

4. Convert the standby database into a snapshot standby database:

( For RAC Configurations: Shutdown all other instances except one, which is used as Snapshot standby database)

SQL>alter database convert to snapshot standby;

5.Shut down the snapshot standby database and startup the database (it will be opened for read/write access):

SQL>shutdown immediate;

SQL>startup

After the Snapshot mode is enabled on the database, perform the required testing and revert back to Physical Standby mode after the testing is complete.

Steps to Revert the Physical Standby Database Back to its Original State

1. Change the standby database back into its standby mode (from snapshot mode) as follows:

SQL>startup mount force;

SQL>alter database convert to physical standby;

SQL>shutdown immediate;

SQL>startup nomount;

SQL>alter database mount standby database;

2. Enable redo log apply.

SQL>alter database recover managed standby database using current logfile disconnect;

3.On the primary database, issue the following statement to re-enable archiving to the physical standby database:

SQL>alter system set log_archive_dest_state_2=enable scope=both;

Protection Modes in Oracle Dataguard

We have 3 Protection modes available in Oracle DataGuard

1. Maximum Performance :

This is the default protection mode. It provides the highest level of data protection that is possible

without affecting the performance of a primary database. This is accomplished by allowing transactions to commit as soon as all redo data generated by those transactions has been written to the online log.

2. Maximum Availability :

This protection mode provides the highest level of data protection that is possible without compromising the availability of a primary database. Transactions do not commit until all redo data needed to recover those transactions has been written to the online redo log and to at least one standby database.

3. Maximum Protection :

This protection mode ensures that no data loss will occur if the primary database fails. To provide this level of protection, the redo data needed to recover a transaction must be written to both the online redo log and to at least one standby database before the transaction commits. To ensure that data loss cannot occur, the primary database will shut down, rather than continue processing transactions.