SHOW ENGINEScommand to view the storage engines supported by the current database:
|Storage Engine||Supported by TencentDB||Reason for Default Disablement|
|MyISAM||Yes (you need to submit a ticket to enable it)||It may cause data inconsistency and affect sync efficiency|
|Archive||Yes (you need to submit a ticket to enable it)||It may cause data inconsistency and affect sync efficiency|
|Federated||No||It may cause security risks|
|CSV||Yes (you need to submit a ticket to enable it)||It may cause data inconsistency and affect sync efficiency|
|PERFORMANCE_SCHEMA||Yes (you need to submit a ticket to enable it)||It may cause data inconsistency and affect sync efficiency|
Notes on TencentDB instance upgrade
During the upgrade of a TencentDB instance, the instance will be disconnected for 1–30 seconds (for switch after upgrade); therefore, you need to get prepared and enable automatic reconnection between your application and database in advance to avoid service unavailability.
Definitions of primary and replica in the documentation
In TencentDB documentation, a replica server refers to the hot backup database server in the high-availability architecture. When the primary server fails, the replica server will be put into use in real time for continuous service.
The architecture of "1 primary-2 replicas" is recommended if strong sync is required
When you perform strong sync replication, the primary database will be hanged if it is disconnected from the replica database or if the replica database fails. If there is only one primary or replica database, the high-availability solution will be unavailable, because if only one single server provides the service, part of the data will be lost completely when a failure occurs.
Enabling public network access for a long time and using weak passwords may lead to security risks
A public network IP of the database is likely to be detected and scanned by malicious users if it is enabled for a long period. If you use a weak password (such as 12345678 or 1234abcd) in this case, your database may be at great security risk.
Notes on TencentDB for MariaDB rollback
Notes on TencentDB locking policy
TencentDB has a locking mechanism. If the storage space usage of your instance exceeds the threshold (which is usually 103–130%; the read-only threshold for TencentDB for MariaDB is 110% currently), the system will lock your instance, which will become read-only. Therefore, we recommend you periodically check the storage space usage and enable SMS reminder for usage in the TencentDB for MariaDB console. If you cannot expand the instance capacity timely for financial reasons, you can submit a ticket to apply for temporary unlocking for 1–3 business days.
TencentDB for MariaDB failover
TencentDB for MariaDB adopts high-availability modes such as 1 primary-1 replica and 1 primary-2 replicas. When the primary fails, TencentDB for MariaDB can switch to the replica within 1 second (200 ms on average). However, during the switch, you cannot access the database for up to 30 seconds (this period of time is used for failure detection and data sync). Therefore, you need to set automatic reconnection between your application and the instance in advance to avoid service unavailability. The switch is imperceptible to the business; that is, the IP and port remain unchanged and no human intervention is required. You only need to ensure that automatic reconnection is enabled for your business.
Things to do after TencentDB instance purchase:
After purchasing a TencentDB instance, you don't need to perform basic Ops tasks, such as high-availability maintenance, backup, and security patch, but you should pay attention to the following:
Check whether the CPU, IOPS, space, and number of connections of your TencentDB instance are sufficient. If they become insufficient, you need to optimize or upgrade the instance.
Check whether your TencentDB instance has performance issues, many slow or poor SQL statements, and excessive or missing indexes.
You cannot modify any data in the
You cannot directly use SQL statements to configure accounts or grant permissions, which can only be done in the console. The following 19 common permissions are supported, while some rarely used permissions are not supported:
SELECT, INSERT, UPDATE, DELETE, CREATE, DROP, REFERENCES, INDEX, ALTER
CREATE TEMPORARY TABLES, LOCK TABLES, EXECUTE, CREATE VIEW, SHOW VIEW
CREATE ROUTINE, ALTER ROUTINE, EVENT, TRIGGER, SHOW DATABASES
TencentDB for MariaDB does not provide the root account
We recommend you use a public network address only for routine maintenance, rather than for connecting business servers