Restrictions on the DR Instance

Updated on 2025-02-17 GMT+08:00

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After a DB instance serves as a DR instance, some basic functions are unavailable and some monitoring metrics cannot be reported. This section describes the restrictions on the DR instance.

Restrictions on the Primary Instance

After a DR relationship is established, the DR instance only allows for storage scaling, specifications change, rebooting, and parameter modification. The basic functions of the primary instance have the following restrictions:

Function	Supported by the Primary Instance During DR
Rebooting an instance	Yes
Modifying parameters	Yes
Applying parameters	Yes
Resetting a password	Yes
Performing a full backup	Yes
Creating a differential backup	Yes
Deleting a backup	Yes
Modifying the backup policy	Yes
Restoring data to the original instance	No
Restoring data to a new instance	Yes
Scaling up storage space	Yes
Adding nodes (only for distributed instances)	No
Changing instance specifications (only for centralized instances)	Yes
Upgrading a minor version	Yes
Viewing slow query logs	Yes
Viewing metrics	Yes
Deleting an instance	No
Deleting an automated backup	N/A
Rebuilding a deleted instance from the recycle bin	N/A
Backing up and restoring data in a single table	Yes
Balancing an instance	Yes
Querying the disk usage	Yes
Creating a database	Yes
Querying a database	Yes
Creating a schema and user	Yes
Deleting a schema and user	Yes
Performing database operations	Yes
Using DAS for database management	Yes
Repairing a node	Yes
Replacing a node	Yes
Forcibly starting a minority of AZs	No
Resuming AZs	No
Switching AZs	Yes
Resetting configurations (for DR)	Yes
Adding replicas	No
Managing tags	Yes
Binding an EIP	Yes

Restrictions on Monitoring Metrics

After the DR relationship is established, some monitoring metrics of the DR instance are unavailable. The following table lists the monitoring metrics of the DR instance.

NOTICE:

If the deployment model of an instance is 1 primary + 1 standby + 1 log, the log node does not have a data disk, and the following node-level metrics related to data disks cannot be displayed for the node:

Disk IOPS
Disk Write Throughput
Disk Read Throughput
Time Required for per Data Disk Write
Time Required for per Data Disk Read

Category	Sub-category	Metric	Displayed for Distributed DR Instance	Displayed for Centralized DR Instance
Instance level	-	Used Instance Disk Size	Yes	No
		Total Instance Disk Size	Yes	No
		Instance Disk Usage	Yes	No
		Deadlocks	No	No
		Response Time of 80% SQL Statements	No	No
		Response Time of 95% SQL Statements	No	No
		Buffer Hit Rate	No	No
Node level	-	CPU Usage	Yes	Yes
		Memory Usage	Yes	Yes
		Data Write Volume	Yes	Yes
		Outgoing Data Volume	Yes	Yes
		Disk IOPS	Yes	Yes
		Disk Write Throughput	Yes	Yes
		Disk Read Throughput	Yes	Yes
		Time Required for per Data Disk Write	Yes	Yes
		Time Required for per Data Disk Read	Yes	Yes
		Swap Memory Usage	Yes	Yes
		Total Swap Memory	Yes	Yes
		IOPS Usage (This metric applies only to nodes that use EVS disks.)	Yes	Yes
		Disk I/O Bandwidth Usage (This metric applies only to nodes that use EVS disks.)	Yes	Yes
Component level	CN	User Logins, User Logouts, Lock Waiting Session Rate, Active Session Rate, CN Connections, User Committed Transactions, User Rollback Transactions, Background Committed Transactions, Background Rollback Transactions, Average Response Time of User Transactions, User Transaction Rollback Rate, Background Transaction Rollback Rate, Data Definition Language, Data Manipulation Language, Data Control Language, DDL and DCL Rate, Data Volume to Be Flushed to Disks, Physical Reads per Second, Physical Writes per Second, Online Sessions, Active Sessions, Online Session Rate, Used Dynamic Memory, Dynamic Memory Usage, Maximum Execution Duration of Database Transactions, Idle Transactions, Slow SQL Statements in the System Database, Slow SQL Statements in the User Database, and Xlog Rate	No	N/A
	Primary DN	Used Disk Size, Total Disk Size, Disk Usage, Data Volume to Be Flushed to Disks, Physical Reads per Second, and Physical Writes per Second	N/A	N/A
	Primary DN	Standby Redo Progress, User Logins, User Logouts, Lock Waiting Session Rate, Active Session Rate, User Committed Transactions, User Rollback Transactions, Background Committed Transactions, Background Rollback Transactions, Average Response Time of User Transactions, User Transaction Rollback Rate, Background Transaction Rollback Rate, Data Definition Language, Data Manipulation Language, Data Control Language, DDL and DCL Rate, Online Sessions, Active Sessions, Online Session Rate, Used Dynamic Memory, Dynamic Memory Usage, Size of WALs Retained in the Replication Slot, and Xlog Rate	N/A	N/A
	Standby DN	Used Disk Size	Yes	Yes
		Total Disk Size	Yes	Yes
		Disk Usage	Yes	Yes
		Primary Node Flow Control Duration	No	No
		Standby Node RTO	No	No
		Standby Node Redo Progress	No	N/A
		Lock-Waiting Session Rate	No	No
		Active Session Rate	No	No
		Online Session Rate	No	No
		Online Sessions	No	No
		Dynamic Memory Usage	No	No

Restrictions on Major Version Upgrade in the DR Mode

Only gray upgrade is supported.

Upgrade the primary instance. Ensure the upgrade is not submitted.
Upgrade the DR instance.
Submit the upgrade of the DR instance first and then the primary instance until the DR instance upgrade is complete

Restrictions on Minor Version Upgrade in the DR Mode

Only gray upgrade is supported.

Upgrade the primary and DR instances at the same time.
Submit the upgrade of the DR instance first and then the primary instance.

NOTICE:

Before submitting the upgrade of the DR instance, ensure that the upgrade of primary instance is complete.
Submit the upgrade of the DR instance first and then the primary instance.
If the DR instance upgrade has been submitted, the upgrade of the primary instance cannot be rolled back.
During the upgrade of the primary and DR instances, do not perform a switchover.

Parent Topic: Disaster Recovery Management

Previous topic: Enabling or Disabling Log Cache

Next topic: Managing GaussDB Tasks

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