GaussDB Constraints

To ensure the stability and security of GaussDB, certain constraints are put in place for access or permissions control. Table 1 describes such constraints.

There is no SLA commitment, so GaussDB single-replica instances cannot be used in production environments. For function constraints of single-replicas, see Table 2.

**Table 1** Function constraints
Function	Constraints
Database access	To access a GaussDB instance that is not publicly accessible, the instance must be in the same VPC subnet as the ECSs associated with the instance. The ECSs must be allowed by the security group to access the GaussDB instance. If a GaussDB instance and the ECSs belong to different security groups, no communication between them is established by default. To allow it, you must add an inbound rule to the GaussDB security group. The default port number of the GaussDB instance is 8000. The database port can be set when a DB instance is created and can be changed after the DB instance is created.
Deployment	ECSs where DB instances are deployed are not directly visible to you. You can only access the DB instances through IP addresses and database ports.
Database root permissions	Only the root user permissions are available on the instance creation page. NOTE: After August 30, 2022, the root user of newly created instances and upgraded existing instances has the sysadmin permission. To upgrade your existing instance, contact technical support. If your existing instances are not upgraded, the root user only has the following permissions: createrole, createdb, and monadmin. The root user has fewer permissions than the administrator. When some SQL syntax or functions, such as create tablespace, are executed, an error message is displayed, indicating that the permissions are insufficient.
GaussDB instance reboot	GaussDB DB instances cannot be rebooted through commands. They must be rebooted on the management console.
GaussDB backup files	GaussDB backup files are stored in OBS buckets and are not visible to you.
Specification changes	By default, the specifications cannot be reduced. If you need to reduce the specifications, contact Huawei Cloud technical support. Before you change the instance specifications, ensure that the instance is available. If the instance or node is abnormal, or the storage space is full, you cannot perform this operation. During the specification change for HA (1 primary + 2 standby) instances, a primary/standby failover is triggered. During the failover, services are interrupted for about 1 minute. For a single-replica instance, changing instance specifications will reboot the instance and interrupt services for 5 to 10 minutes. Changing the CPU and memory specifications will cause the instance to reboot, services will be temporarily interrupted during the reboot.
Failover	For primary/standby instances, services are unavailable for about 10 seconds when the primary node is being switched to the standby node.
Data restoration	To prevent data loss, you are advised to back up key data before data restoration.
Storage space	If the storage space of an instance is full, data cannot be written to databases. You are advised to periodically check the storage space.
Performance tuning	Performance tuning may need to reboot the instance and interrupt services.

**Table 2** Function constraints of single-replica primary/standby instances
Function	Supported by Versions Earlier Than 3.0	Supported by 3.0 and Later
Creating an instance	Yes	Yes
Restarting a DB instance	Yes	Yes
Modifying parameters	Yes	Yes
Applying parameters	Yes	Yes
Resetting a password	Yes	Yes
Creating a full backup	No	Yes
Creating a differential backup	No	Yes
Deleting a backup	No	Yes
Modifying the backup policy	No	Yes
Restoring data to the original instance	No	Yes
Restoring data to a new instance	No	Yes
Restoring data to an existing instance	No	Yes
Scaling up storage	Yes	Yes
Changing CPU and memory specifications of an instance	Yes	Yes
Hot patch upgrade	No	Yes
In-place upgrade	Yes (The version can be upgraded only to 3.0 or later.)	Yes
Gray upgrade	No	Yes (only supported in version 3.207 or later)
Viewing monitoring metrics	Yes	Yes
Deleting an instance	Yes	Yes
Rebuilding a deleted instance	No	Yes
Querying the disk usage	Yes	Yes
Creating a database	Yes	Yes
Querying a database	Yes	Yes
Creating a schema and user	Yes	Yes
Deleting a schema and user	Yes	Yes
Performing database operations	Yes	Yes