This topic provides a list of common questions you may ask about ApsaraDB for RDS and their corresponding answers.

What is a database instance?

A database instance is a database server on which you can create one or more databases. Each database can house one or more tables.

What are primary and secondary instances?

In the High-availability, Cluster, or Enterprise Edition, your database system consists of one primary instance and one or two secondary instances. The primary instance is used to communicate with your applications. A secondary instance serves as a backup and does not provide database services as long as the primary instance is functional.

The primary instance replicates data to its secondary instance in real time. When the primary instance becomes abnormal, its secondary instance takes over the services from it. In such cases, the primary instance is demoted as a secondary instance while its secondary instance is promoted as the primary instance. Your business remains available except a possible transient disconnection.

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

What are read-only instances?

Read-only instances are provided to scale the read capability of your database system. If a large number of read requests overwhelm the primary instance, you can create one or more read-only instances to offload read requests from it.

For more information, see Overview of ApsaraDB RDS for MySQL read-only instances.

Why am I charged additional fees for a subscription instance?

The fee you pay when you purchase a subscription instance only covers the instance and its storage capacity. If you create read-only instances, enable SQL Explorer or performance monitoring, or consume more storage usage than allowed by the free tier of backup space, you must pay the additional fees incurred. For more information, see Pricing, billing items, and billing methods.

After I purchase an RDS instance, the ApsaraDB for RDS console does not respond nor can I find the RDS instance I created. Why?

There are two possible reasons:

  • The RDS instance you created does not reside in the region you selected.

    In the top navigation bar, select the region where the RDS instance resides. Then you can find the RDS instance you created.

    Select a region
  • The zone you selected cannot provide sufficient resources.

    Resources in zones are dynamically allocated. After you confirm the purchase order, the zone you selected may fail to provide sufficient resources. As a result, the instance creation fails. We recommend that you select another zone and try again. You can visit the Orders to check for the fees returned to you.

Will I be charged for a pay-as-you-go instance that I am not using?

Yes, your pay-as-you-go instance consumes computing and storage resources even if you are not using it, therefore you are still charged an hourly fee. If you will not use your pay-as-you-go instance for a long period of time, we recommend that you save its data and then release it.

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

Yes, you can switch between subscription billing and pay-as-you-go billing. For more information, see Switch the billing method from pay-as-you-go to subscription and Switch the billing method from subscription to pay-as-you-go.

How much do I need to pay if I change the specifications of a subscription instance?

For more information, see Specification change fees.

What will happen if a subscription instance expires or its payment is overdue?

For more information, see Impact of expiration and overdue payment.

Is the Internet traffic that involves inbound and outbound traffic consumed for my pay-as-you-go and subscription instances free of charge?

Yes, all Internet traffic that involves inbound and outbound traffic consumed for your pay-as-you-go and subscription instances is free of charge.

Do I need to pay if I apply for a public endpoint?

No, you are not charged when you apply for a public endpoint.

Why does an entry-level instance support a larger maximum number of connections and deliver higher input/output operations per second (IOPS) than an enterprise-level instance when they have the same CPU and memory specifications?

An entry-level instance belongs to the general-purpose instance or shared instance family, whereas an enterprise-level instance belongs to the dedicated instance family. The general-purpose instance and shared instance families support reuse of CPU resources, which enables an entry-level instance to support a larger maximum number of connections and deliver higher IOPS. However, the dedicated instance family supports exclusive CPU and memory resources, and therefore an enterprise-level instance is more stable. For more information, see Overview.

How do I authorize a RAM user to manage my RDS instance?

For more information, see Use RAM to manage ApsaraDB for RDS permissions.

How do I change the storage type of my RDS instance between local SSD, standard SSD, and enhanced SSD?

For more information, see How to change a cloud disk to a local disk

How long does it take to expand the storage capacity of my RDS instance?

The time taken varies depending on whether the remaining storage capacity of the physical host that houses your RDS instance is sufficient for your expansion plan. If the remaining storage capacity is insufficient, you must migrate your RDS instance to another qualified physical host before you start the expansion. This is time-consuming. If the remaining storage capacity is sufficient, you do not need to migrate your RDS instance and therefore the time taken is short.

Will the system automatically upgrade the specifications of read-only instances after I upgrade the specifications of their primary RDS instance?

No, you must upgrade the specifications of read-only instances manually.

Will my online services be interrupted while I change the specifications of my RDS instance?

While you change the specifications of your RDS instance, only a 30-second transient disconnection may occur.

Will the endpoints and addresses of my RDS instance change after I change its specifications?

After you change the specifications of your RDS instance, its internal and public endpoints and read/write splitting endpoint remain unchanged, but the corresponding IP addresses may change. We recommend that you use the internal endpoint, public endpoint, or read/write splitting endpoint of your RDS instance to establish a connection from your application.

How do I change the VPC of my RDS instance?

  • You can change the VPC and VSwitch if your RDS instance supports the change. For more information, see Switch to a new VPC and VSwitch for an RDS MySQL instance.
  • If your RDS instance supports direct network type changes:
    1. Switch the network type from VPC to Classic Network.
    2. Switch the network type from Classic Network to VPC with the destination VPC selected.
  • If your RDS instance does not support direct network type changes:

    Purchase a new RDS instance with the destination VPC selected, and then migrate data to the new RDS instance. For more information, see Migrate data between ApsaraDB for RDS instances.

Can I communicate with a secondary instance?

No, you can only communicate with a primary instance. A secondary instance serves only as a backup and does not provide services.

Does an IP address whitelist take effect immediately after it is configured?

An IP address whitelist takes effect about 1 minute after it is configured.

Why do I find IP address whitelists that I have not created?

If the IP address whitelists consist of internal IP addresses, they were probably created by other Alibaba Cloud products such as DMS and DAS. They do not affect your data and you do not need to take actions on them.

IP address whitelist created by DAS

Is my RDS instance exposed to security risks if I only enable internal network access and disable Internet access?

We recommend that you change the network type of your RDS instance to VPC. Only ECS instances in the same VPC can access your RDS instance after their IP addresses are added to the whitelists. For more information, see Change the network type of an ApsaraDB RDS for MySQL instance.

If I do not update its expired SSL certificate, will my RDS instance malfunction or its data security deteriorate?

If you do not update the SSL certificate after it expired, your RDS instance can still run and its data security does not deteriorate. However, the applications that use encrypted connections to communicate with your RDS instance are disconnected.

How do I obtain the size of SQL logs generated by SQL Explorer?

Log on to the ApsaraDB for RDS console, find the target RDS instance, and navigate to the Basic Information page. Then, in the Usage Statistics section, view the size of SQL logs generated by SQL Explorer.

Log Size for SQL Explorer

Can applications that reside outside the VPC where my RDS instance is housed communicate with my RDS instance?

If the IP addresses of the applications are added to the whitelists of your RDS instance, these applications are granted access to your RDS instance no matter whether they reside in VPCs or the classic network. For more information, see Configure a whitelist for an ApsaraDB RDS for MySQL instance.

Can I manage accounts at fine-grained levels such as source address and table levels?

You can log on to the target database and then use commands to grant accounts the permissions to manage it at fine-grained levels. For more information about how to log on to a database, see Connect to an ApsaraDB RDS for MySQL instance.

What are the unique permissions that privileged and standard accounts have?

For more information, see Create accounts and databases for an ApsaraDB RDS for MySQL instance.

Does ApsaraDB for RDS provide accounts equivalent to root or super users?

To protect your RDS instance from damages such as data loss and leaks caused by incorrect operations, ApsaraDB for RDS does not provide accounts equivalent to root or super users.

Can I manage the accounts created in a primary instance from its read-only instances?

No, although the accounts created on a primary instance are synchronized to its read-only instances, they cannot be managed on the read-only instances. Additionally, the accounts only have read permissions on the read-only instances.

Will the system automatically upgrade the specifications of read-only instances after I upgrade the specifications of their primary RDS instance?

No, you must manually upgrade the read-only instances of a primary instance. For more information, see Change specifications.

Can I choose subscription billing for read-only instances?

No, read-only instances only support pay-as-you-go billing. This make it easier for you to change the instance specifications.

Can I access a read-only instance with a read weight of 0?

No, you can only access a read-only instance by using its own internal or public endpoint after you set its read weight to 0. We recommend that you set the read weight of a read-only instance to 0 when you want this read-only instance to serve only a specific service.

If I release a read-only instance, will my database services be interrupted?

Yes, if you release a read-only instance, your database service will be interrupted. We recommend that you set the read weight of the read-only instance to 0 before you release it. The previously cached connection with your database system remains valid on the released read-only instance until you terminate this connection and establish a new one.

What do I do if read/write splitting goes wrong?

For more information, see FAQ for read/write splitting.

Can I disable data backup for an ApsaraDB RDS for MySQL instance?

No, you cannot disable data backup for an ApsaraDB RDS for MySQL instance. However, you can lower the data backup frequency to at least twice a week. The data backup retention period must be at least seven days.

Can I disable log backup for an ApsaraDB RDS for MySQL instance?

If the ApsaraDB RDS for MySQL instance is not in the Basic Edition, you can disable log backup for it in the ApsaraDB for RDS console.

Why does a backup task fail?

If you perform data definition language (DDL) operations while you execute a backup task, the DDL operations trigger table locks that cause the backup task to fail.

Why do I find two binary log files with the same name on the Log Backup tab?

In the High-availability Edition, your database system consists of a primary instance and a secondary instance. The primary and secondary instances both generate binary log files. Each binary log file is identified by an Instance ID on the Log Backup tab. You can distinguish the binary log files generated by the primary instance from those generated by the secondary instance based on their instance IDs. On the Service Availability page, you can view the primary instance ID under Primary Instance Number and the secondary instance ID under Secondary Instance Number.

Primary Instance Number and Secondary Instance Number

What can I do with the data backup file or binary log file that I downloaded?

You can use a data backup file or binary log file to restore data at any time. For more information, see Use a physical backup file to restore an ApsaraDB RDS for MySQL instance to a user-created MySQL database or Restore data from logical backup files of an ApsaraDB RDS MySQL instance to an on-premises database.

Why is it that an instance that stores a small amount of data has a snapshot that is much larger?

When the system creates a snapshot, the system eliminates empty blocks to reduce the size of the snapshot. A block occupies 2 MB of storage space. However, data may be distributed across a large number of blocks. For example, assume that you have 3 MB of data distributed in more than two blocks. The snapshot size will be calculated as the storage space occupied by all blocks that store data and the snapshot size will be large than the original data size.