Help Center/ GaussDB/ User Guide/ Cross-Cloud DR Management/ Restrictions on the DR Instance
Updated on 2024-12-25 GMT+08:00

Restrictions on the DR Instance

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

Scaling down storage space

Y

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.

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

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.

  1. Upgrade the primary instance. Ensure the upgrade is not submitted.
  2. Upgrade the DR instance.
  3. 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.

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