Overview
Last updated: 2025-10-11 10:33:52
TencentDB for SQL Server supports flexible scaling that allows you to quickly adjust instance architecture, version, and specification in the console. You can do so at any time (at the start, during rapid development, or during peak/off-peak hours), so you can get the most out of your resources and reduce unnecessary costs in real time.
Prerequisites
You can adjust the configuration of a TencentDB for SQL Server instance and its associated instances only when they are in running status and are not executing any tasks.
Adjustment item
Adjustment Item | Description |
Architecture | Single-node (formerly Basic Edition) instances cannot be upgraded to two-node (formerly High Availability/Cluster Edition) instances. If needed, you can purchase new two-node instances and migrate the data with DTS. The two-node edition (formerly HA/Cluster Edition) does not support upgrading to the multi-node edition. This feature will be supported in the future. You can upgrade in the console when the feature is supported. |
Version | Version upgrade is supported for the single-node edition (formerly Basic Edition), two-node edition (formerly HA/Cluster Edition), and multi-node edition. To upgrade the version of a two-node (formerly High Availability/Cluster Edition) instance associated with a read-only instance, disassociate the read-only instance first before upgrading or submit a ticket for assistance. |
Instance specification | All instance types support specification upgrade and downgrade. The upper limit of disk capacity under the corresponding specification is as displayed on the Adjust Configuration page in the console. |
Disk capacity | Single-node (formerly Basic Edition) instances support disk capacity expansion but not reduction. Two-node (formerly High Availability/Cluster Edition) instances of local disk edition support disk capacity expansion and reduction. Two-node (formerly High Availability/Cluster Edition) instances of cloud disk edition support disk capacity expansion but not reduction. The multi-node edition supports expanding the disk capacity but not shrinking the disk capacity. |
Note:
If you need to horizontally scale the read capability of your database, use read-only instances to mitigate the pressure on the primary instance as instructed in Managing Read-Only Instance.
Restrictions on upgrade/downgrade
Instance Type | Disk Type | Version Upgrade | Architecture Upgrade | Specification Upgrade | Disk Capacity Expansion | Version Downgrade | Architecture Downgrade | Specification Downgrade | Disk Capacity Reduction |
Single-node (formerly Basic Edition) instance | Cloud disk | ✓ | X | ✓ | ✓ | X | X | ✓ | X |
Two-node (formerly High Availability/Cluster Edition) instance | Local disk | ✓ | ✓ | ✓ | ✓ | X | X | ✓ | ✓ |
| Cloud disk | ✓ | ✓ | ✓ | ✓ | X | X | ✓ | X |
Multi-node | Cloud disk | ✓ | X | ✓ | ✓ | X | X | ✓ | X |
Read-only instance | Local disk | X | X | ✓ | ✓ | X | X | ✓ | ✓ |
| Cloud disk | X | X | ✓ | ✓ | X | X | ✓ | X |
Instance disk space description
Single-node (formerly Basic Edition) instance - cloud disk
When the size of the data stored in an instance exceeds its storage space, the database will become read-only. We recommend that you check the disk monitoring metrics of the instance in time as instructed in Viewing Monitoring Charts, set the alarm policy for the disk in CM, and expand the storage space or delete tables in the console promptly, so as to prevent the read-only status from affecting your business operations. The instance will become readable/writable after your expand or free up the storage space.
Two-node (formerly High Availability/Cluster Edition) instance - local disk
When the size of the data stored in an instance exceeds its storage space, features such as database import and rollback will become unavailable. You will need to expand its capacity or delete some database tables in the console to release the storage space. We recommend that you check the disk monitoring metrics of the instance in time as instructed in Viewing Monitoring Charts and set the alarm policy for the disk in CM, so as to prevent disk overruns from affecting your business operations.
Two-node (formerly High Availability/Cluster Edition) instance - cloud disk
When the size of the data stored in an instance exceeds its storage space, the database will become read-only. We recommend that you check the disk monitoring metrics of the instance in time as instructed in Viewing Monitoring Charts, set the alarm policy for the disk in CM, and expand the storage space or delete tables in the console promptly, so as to prevent the read-only status from affecting your business operations. The instance will become readable/writable after your expand or free up the storage space.
Multi-node instance - cloud disk
After the volume of data stored in the instance exceeds the storage space purchased for the instance, the instance will become read-only. (Data can only be read but not written.) It is recommended that you view the disk monitoring data of the instance in time through monitoring charts and set an alarm policy for disks on Tencent Cloud Observability Platform (TCOP). If an alarm is triggered, you can scale out the instance or delete some database tables via the console to release storage space to prevent the instance from becoming read-only and ensure normal business operation. Data read/write becomes normal immediately after the instance is scaled out or storage space is released.
Configuration adjustment rules
You cannot cancel a configuration adjustment operation in progress.
The name, access IP, and access port of an instance will remain the same after configuration adjustment.
Data migration may be involved in configuration adjustment. During data migration, the TencentDB for SQL Server instance can be accessed normally and the business will not be affected.
Note:
Due to business security and risk control requirements, the system may prompt you to restart the instance to lift the feature limitations when you perform the configuration adjustment operation on instances and data migration is involved. At this point, follow the prompt in the console to complete the instance restart before you perform the configuration adjustment operation.
Instance switchover may be needed after configuration adjustment is completed (i.e., the TencentDB for SQL Server instance may be disconnected for seconds). We recommend that you use applications configured with automatic reconnection feature and conduct the switch during the instance maintenance time. For more information, see Setting Instance Maintenance Information.
Limits
Instances of the single-node edition (formerly Basic Edition) have only one database node but no replica node for hot backup. Therefore, instance services become unavailable for a long time if the node goes down or a configuration change or version upgrade task is executed. If the business has relatively high availability requirements for the database, the single-node edition (formerly Basic Edition) is not recommended. You can choose the two-node edition (formerly HA/Cluster Edition) or the multi-node edition.
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