Q&A

Basic concepts

• What is a database instance?

  A database instance is a database server. You can create one or more databases on an instance. You can create one or more tables in each database.

• What are primary and secondary instances?

  For High-availability Edition, SQL Server Cluster Edition instances, the node that your application accesses is the primary instance. Data from the primary instance is synchronized in real time to another node, which is the secondary instance.

  You can only access the primary instance. The secondary instance serves only as a backup and does not handle service requests. If the primary instance fails, an instance switchover occurs. The secondary instance becomes the primary instance, and the original primary instance becomes the secondary instance and is rebuilt. The switchover process is transparent to your application, but a transient disconnection may occur.

  Note

  In RDS MySQL Cluster Edition instances, the nodes are called primary and secondary nodes. The secondary nodes are readable. If the primary node fails, any secondary node can be promoted to the primary node.

  For more information about the primary and secondary instances for each edition, see Overview of ApsaraDB RDS instance editions.

• What is a read-only instance?

  A read-only instance provides read scalability and offloads read requests from your primary instance. In scenarios with a high volume of read requests and a low volume of write requests, a single instance may be unable to handle the read workload, which can affect your services. In this case, you can create one or more read-only instances to handle the high volume of read requests and increase the throughput of your application.

  For more information, see Introduction to ApsaraDB RDS for MySQL read-only instances.

Billing and purchase

• Why do I receive an "insufficient permissions" error when I create an RDS instance?

  This issue often occurs when a Resource Access Management (RAM) user tries to create an RDS instance. To create an RDS instance, use an Alibaba Cloud account. If you must use a RAM user to create an instance, grant the AliyunRDSFullAccess permission to the RAM user. For more information, see RAM resource authorization.

• My instance is a subscription instance. Why are there other charges?

  The subscription fee covers only the instance and storage space. If you use read-only instances, SQL Explorer, or paid performance monitoring features, or if your backup storage usage exceeds the free quota, you will incur additional charges. For more information, see Billing items.

• Why is there no response after I try to create an instance, and the instance does not appear in the instance list?

  This may happen for two reasons:

  • Incorrect region

    The region that is selected in the console may be different from the region in which you created the instance. You can switch regions in the upper-left corner of the page.

    

  • Insufficient resources in the zone

    Zone resources are dynamically allocated. The resources in the selected zone may be insufficient when you place an order. This can cause the instance creation to fail. You can try to create the instance in a different zone. If the creation fails, a refund is issued. You can find the refund details in the Orders list.

• Are pay-as-you-go and Serverless instances charged even when they are not in use?Are pay-as-you-go instances charged even when they are not in use?

  Yes. Because a pay-as-you-go or Serverless instance continues to reserve compute and storage resources when idle, you are still charged hourly. If you do not plan to use your RDS MySQL or RDS PostgreSQL instance for an extended period, suspend it. After an instance is suspended, its compute resources are released and specification fees no longer apply. For more information, see Suspend an ApsaraDB RDS for MySQL instance or Suspend an ApsaraDB RDS for PostgreSQL instance.

• Can I switch between the subscription and pay-as-you-go billing methods?

  Yes, you can. For more information, see Switch from pay-as-you-go to subscription and Switch from subscription to pay-as-you-go.

• Can I release a subscription instance?

  You cannot release a subscription instance. However, you can unsubscribe from the instance to receive a refund. Refunds are available for three scenarios: 5-day money-back guarantee, standard unsubscription, and unsubscription from a pending renewal order. For more information about the rules, see Rules for unsubscribing from a product.

• How are configuration changes for subscription instances billed?

  For more information, see Change configuration.

• What happens if my instance expires or has an overdue payment?

  For more information, see Overdue payments.

• Is Internet traffic free for both pay-as-you-go and subscription instances? Is both inbound and outbound traffic free?

  Yes, Internet traffic is free for both pay-as-you-go and subscription instances. This applies to both inbound and outbound traffic.

• Is there a fee for applying for a public endpoint?

  No, applying for a public endpoint is free of charge.

• Why do general-purpose instance types have higher maximum connections and IOPS than dedicated instance types with the same CPU and memory?

  This is because general-purpose instance types belong to the shared instance family, while dedicated instance types belong to the dedicated instance family. In practice, dedicated instance types are more stable because they have dedicated CPU and memory resources. For more information about the differences, see Instance families.

Instance management

• How do I grant a RAM user permissions to manage RDS instances?

  For more information, see Grant permissions on ApsaraDB RDS.

• How do I change the virtual private cloud (VPC)?

  • Some RDS MySQL instances support changing the VPC and vSwitch directly. For more information, see Switch the VPC and vSwitch.

  • Cloud disk instances with a minor engine version earlier than 20201031 do not support changing the VPC directly. You can use one of the following methods to change the VPC.

    • Upgrade the minor engine version, and then refer to this document for the changes.

    • If you do not want to upgrade the minor kernel version, please purchase an ApsaraDB RDS for MySQL instance (select the destination VPC at the time of purchase), and then Migrate your data to the new instance.

• Can I access the secondary instance?

  No, you cannot. You can only access the primary instance. The secondary instance serves only as a backup and does not handle service requests.

• When using a VPC, how many private IP addresses does an RDS MySQL instance occupy?

  The number of private IP addresses used varies by instance type because of the underlying implementation:

  • RDS MySQL 5.5, 5.6, 5.7, and 8.0 High-availability Edition (local SSD): 1

  • RDS MySQL 5.7 Basic Edition (standard SSD): 1

  • RDS MySQL 8.0 Basic Edition (standard SSD): 2

  • RDS MySQL 5.7 and 8.0 High-availability Edition (cloud disk): 3

• How do I stop an RDS instance that I am not using temporarily?

  ApsaraDB RDS does not support stopping an instance. If you do not need to use an instance for a period of time, you can migrate the database to a local machine and then release the instance. For more information, see Release or unsubscribe from an instance.

Configuration changes

• What do I do if my instance is locked due to insufficient storage space?

  For more information, see What do I do if the instance status is "Locked"?.

• What do I do if the instance disk is full?

  • You can enable automatic storage expansion. This feature automatically expands the disk space when it is insufficient, which prevents your instance from being locked. For more information, see Enable automatic storage expansion for an RDS MySQL instance and Enable automatic storage expansion for an RDS PostgreSQL instance.

  • You can manually expand the storage space of the instance. For more information, see Change configuration.

• When I upgrade the configuration of a primary instance, is the configuration of its read-only instances automatically upgraded?

  You must manually upgrade read-only instances because they are not automatically upgraded.

• How do I change the storage type (local SSD, standard SSD, and enterprise SSD)?

  For more information, see How do I change the storage type from cloud disk to local SSD?.

• How long does it take to expand storage space?

  The system checks if the instance's host has enough storage space for the expansion. If it does, the expansion is performed without data migration and is completed quickly. If not, the system migrates the data to a host with sufficient storage space, which takes more time.

• Will changing the configuration affect my online services?

  A transient disconnection of about 30 seconds occurs during the switchover.

• Will the instance endpoints change after I change the configuration?

  The internal/public endpoints and the read/write splitting endpoint will not change, but their corresponding IP addresses may change. We recommend that you use the endpoints in your application.

• What do I do if I keep getting an "out of stock" error when I try to upgrade storage space?

  You can migrate the instance to another zone and then upgrade the storage space. Migrating the instance to another zone does not change the connection endpoint, but the corresponding IP address will change. We recommend that you configure your application to automatically reconnect.

Security

• Do IP whitelist settings take effect immediately?

  After you configure a whitelist, the settings take effect in about one minute.

• Why are there new, unfamiliar whitelist groups?

  If the new groups contain internal IP addresses, they are typically whitelists automatically generated by other Alibaba Cloud services, such as DMS or DAS, to support certain console features. No action is required from you. These whitelists do not affect your data.

• If I do not enable public access and only use internal access, are there still security risks?

  We recommend that you switch your RDS instance to a VPC for better security. In a VPC, an RDS instance can be accessed only by ECS instances that are in the same VPC and whose internal IP addresses are added to the RDS instance's whitelist.

• What happens when an SSL certificate expires? Does the expired certificate affect instance operation or data security?

  If you do not renew an expired SSL Certificate, clients that use encrypted connections will be unable to connect to the instance. This does not affect the operation of the instance or the security of your data.

Audit issues

After I enable SQL Explorer, how do I check the size of the logs it generates?

Connections

• How do I resolve issues with connecting to an instance?

  For more information, see Troubleshoot ApsaraDB RDS for MySQL connection failures.

• Can an instance in a VPC be accessed from the internet?

  Once you have connected to an RDS MySQL instance using a client or the command line, you can access instances in virtual private clouds (VPCs) and classic networks from the internet.

• Does a primary/secondary switchover affect the connection endpoint?

  A primary/secondary switchover does not change the connection endpoint. However, the underlying IP address changes. This change does not affect the normal operation of your application.

Account and database

• Can I manage accounts with finer granularity (such as restricting source addresses or table access)?

  You can connect to the database and then run commands to grant more specific permissions.

• What are the specific permissions of privileged accounts and standard accounts?

  For more information, see Account permissions.

• Does ApsaraDB RDS provide a root account or super privileges?

  ApsaraDB RDS does not provide a root account or an account with superuser privileges. This restriction is in place to prevent irreversible data loss or leaks that may result from misoperations.

• Can an account created on a primary instance be used on a read-only instance?

  Yes. Accounts created on the primary instance are synchronized to its read-only instances. You cannot manage accounts directly on a read-only instance. On a read-only instance, these accounts can only perform read operations.

Read-only instance and read/write splitting

• When I upgrade the configuration of a primary instance, is the configuration of its read-only instances automatically upgraded?

  To upgrade read-only instances, you must manually change configuration.

• If I set the read weight of a read-only instance to 0, can I still access it?

  Yes, but not through the read/write splitting endpoint. You can access the instance only using its internal or public endpoint. This method is typically used to dedicate a read-only instance to a specific service.

• Will releasing a read-only instance affect my services?

  Yes, it will. We recommend that you first set the read weight of the read-only instance to 0 and then release the instance. Existing cached connections may still be directed to the read-only instance. New connections are required to be routed to other read-only instances.

• What do I do if I encounter issues with read/write splitting?

  For more information, see Read/write splitting FAQ.

• The write frequency on my primary instance is low. Can I also send read requests to the primary instance?

  When you set the read weight, you must also set a weight for the primary instance.

Backup and recovery

• Can you disable MySQL data backup?

  No, you cannot. You can reduce the backup frequency, but you must perform at least two backups per week. The minimum retention period for data backups is 7 days.

• Can you disable MySQL log backup?

  Yes, you can, except for Basic Edition instances. You can disable log backups in the backup settings.

• Why do backup jobs sometimes fail?

  Executing DDL operations during a backup can cause table locks, which can cause the backup to fail.

• In log backups, why are there two files with the same binary logging (Binlog) file name?

  High-availability Edition instances use a primary/secondary architecture. Both the primary and secondary instances generate Binlog files. You can distinguish between them using the Instance ID of the Binlog field. You can view the IDs of the primary and secondary instances on the Service Availability page.

• What is the purpose of downloaded data backups and log backups?

  You can use these backup files to restore data to a self-managed database at any time. For more information, see Restore data from physical backup files of an RDS MySQL instance to a self-managed database or Restore data from logical backup files of an RDS MySQL instance to a self-managed database.

• Why is my snapshot backup much larger than the actual data size? For example, why is a snapshot backup tens of GB when the data is only a few GB? Snapshots back up data at the block level. Although empty blocks are skipped during a snapshot backup, any block that contains data is backed up in its entirety. Each block has a fixed size of 2 MB. If data is written to the disk in a scattered manner, a small amount of data can cause many blocks to be only partially filled. For example, 3 MB of data might occupy two, three, or even four separate blocks. The size of the snapshot backup is the total size of all these non-empty blocks. As a result, the snapshot backup can be significantly larger than the actual size of the data itself.

• How can I quickly and easily query data in a backup file?

  For full logical backup files, you can use the backup set query feature of Data Disaster Recovery. This feature lets you directly query data in backup sets stored in cloud storage without restoring the backup data.

Migration and synchronization

For more information, see DTS FAQ.