Updated on 2025-08-04 GMT+08:00

Constraints

The following tables list the constraints designed to ensure stability and security of GeminiDB Cassandra instances.

Specifications

Table 1 Specifications

Resource Type

Specifications

Description

CPU and memory

GeminiDB Cassandra cluster instances are supported.

Storage Space

The storage space depends on the selected instance specifications.

Storage capacity can be scaled up or down. For details, see Overview.

Quotas

Table 2 Quotas

Resource Type

Constraint

Description

Tag

A maximum of 20 tags can be added for each instance.

For more information, see Managing GeminiDB Cassandra Instance Tags.

Free backup space

GeminiDB Cassandra instances provide free backup storage.

For more information, see Backup Storage.

Retention period

The default value is 7 days. The value ranges from 1 to 3660 days.

For more information, see Automated Backup Policy.

Naming Rules

Table 3 Naming rules

Item

Description

Instance name

  • Can contain 4 to 64 characters.
  • Must start with a letter. Only letters (case-sensitive), digits, hyphens (-), and underscores (_) are allowed.

Backup name

  • Can contain 4 to 64 characters.
  • Must start with a letter. Only letters (case sensitive), digits, hyphens (-), and underscores (_) are allowed.

Parameter template name

  • Can contain 1 to 64 characters.
  • Only letters (case sensitive), digits, hyphens (-), underscores (_), and periods (.) are allowed.

Security

Table 4 Security

Item

Description

Password of database administrator rwuser

  • Can contain 8 to 32 characters.
  • Can contain at least two types of the following characters: uppercase letters, lowercase letters, digits, and special characters ~!@#%^*-_=+? For more information, see Resetting the Administrator Password.
  • Keep your password secure. The system cannot retrieve it if it is lost.

Database port

Database port number.

When creating a GeminiDB Cassandra instance, you cannot specify a port number. The default port number is 8635.

The port number can be changed after the instance is created.

The database port ranges from 2100 to 9500 except 2180, 2181, 2887, 3887, 7000, 7001, 7199, 8000, 8018, 8079, 8091, 8092, 8479, 8484, 8636, and 8999.

VPC

After a GeminiDB Cassandra instance is created, the VPC where the instance is deployed cannot be changed.

Intranet security group

A security group controls access between GeminiDB Cassandra API and other services. Ensure that the security group you selected allows your client to access the instance.

If no security group is available, the system creates one for you.

Instance Operations

Table 5 Instance operations

Function

Constraint

Database access

  • If remote access is not enabled, GeminiDB Cassandra instances and their associated ECSs must be in the same VPC subnet.
  • The security group must allow access from the associated ECS.

    By default, a GeminiDB Cassandra instance cannot be accessed through an ECS in a different security group. You need to add an inbound rule to the security group.

  • The default port number of a GeminiDB Cassandra instance is 8635.
  • The database port can be changed only after the instance is created.

Instance deployment

The servers where instances are deployed are not directly visible to you. You can only access the instances through IP addresses and database ports.

Restarting a GeminiDB Cassandra instance

  • GeminiDB Cassandra instances cannot be rebooted through commands. They must be rebooted on the console.
  • Restarting an instance will interrupt services, so off-peak hours are the best time. Ensure that your application can be reconnected.

Viewing GeminiDB Cassandra instance backups

GeminiDB Cassandra instance backups are stored in OBS buckets and are invisible to you.

Changing the CPU or memory of a GeminiDB Cassandra instance

  • Second-level intermittent disconnection occurs once when the specifications are changed on a single node. Therefore, the entire instance is intermittently disconnected several times. Ensure that the client can be reconnected. You are advised to change the specifications during off-peak hours.
  • For a node whose specifications are being changed, its computing tasks are handed over to other nodes. Change specifications of nodes during off-peak hours to prevent instance overload.

Data restoration

To prevent data loss, you are advised to back up key data before data restoration.

Storage

If the storage space of an instance is full, data cannot be written to databases. You are advised to periodically check the storage space.

GeminiDB Cassandra instance storage can be automatically scaled up in case of a sudden surge in data volumes. Enable autoscaling by following Automatically Scaling Up Storage Space.

Recycle bin

  • You can move unsubscribed yearly/monthly instances and deleted pay-per-use instances to the recycle bin. You can restore an instance that was deleted up to 7 days ago from the recycle bin.
  • The recycling policy is enabled by default and cannot be disabled. Instances in the recycle bin are retained for 7 days by default, and this will not incur any charges.
  • Currently, you can put a maximum of 100 instances into the recycle bin.
  • If you delete an instance running out of storage, it will not be moved to the recycle bin.

For details about other development and O&M specifications that can effectively evaluate and improve service system stability, see Database Rules.