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This operation must meet the following requirements:

The master instance must use one of the following database engine versions or editions:
- MySQL 5.6
- MySQL 5.7/8.0 High-availability Edition (based on local SSDs)
- SQL Server 2017 Cluster Edition
For MySQL instances:
- If the memory of the master instance is greater than or equal to 64 GB, the master instance can have up to 10 read-only instances.
- If the memory of the master instance is less than 64 GB, the master instance can have up to five read-only instances.
For SQL Server instances, the master instance can have up to seven read-only instances.

Debugging

You can use OpenAPI Explorer to perform debugging. OpenAPI Explorer allows you to perform various operations to simplify API usage. For example, you can retrieve APIs, call APIs, and dynamically generate SDK example code.

Request parameters


Parameter	Type	Required	Example	Description
Action	String	Yes	CreateReadOnlyDBInstance	The operation that you want to perform. Set this parameter to CreateReadOnlyDBInstance.
RegionId	String	Yes	cn-hangzhou	The ID of the region. The read-only instance and the master instance must be in the same region. You can call the DescribeRegions API operation to view the latest regions.
ZoneId	String	Yes	cn-hangzhou-b	The ID of the zone. You can call the DescribeRegions API operation to view the latest zones.
DBInstanceId	String	Yes	rm-uf6wjk5xxxxxxx	The ID of the master instance.
DBInstanceClass	String	Yes	rds.mys2.small	The type of the instance. For more information, see Instance types. The type of the read-only instance must be no less than that of the master instance. Otherwise, the read-only instance incurs high latency and high load.
DBInstanceStorage	Integer	Yes	20	The storage space of the instance. Value range: 5 to 3000. The value must be a multiple of 5. Unit: GB. Note Instances of different versions have different value ranges. For more information, see the read-only instance creation page in the console.
EngineVersion	String	Yes	5.6	The version of the database. The database and the master instance must have the same database version. Valid values: 5.6 5.7 8.0 2017_ent
PayType	String	Yes	Postpaid	The billing method. The system only supports Pay-As-You-Go. Valid value: Postpaid.
DBInstanceDescription	String	No	Read-only instance for test	The description of the instance. The description must be 2 to 256 characters in length and can contain letters, digits, underscores (_), and hyphens (-). It must start with a letter. Note It cannot start with http:// or https://.
ClientToken	String	No	ETnLKlblzczshOTUbOCzxxxxxxxxxx	The client token that is used to guarantee the idempotency of requests. The client token is generated by the client and is unique among different requests. It is a string of up to 64 ASCII characters.
InstanceNetworkType	String	No	Classic	The network type of the instance. Valid values: VPC Classic Default value: Classic.
VPCId	String	No	vpc-uf6f7l4fg90xxxxxxxxxx	The ID of the VPC.
VSwitchId	String	No	vsw-uf6adz52c2pxxxxxxxxxx	The ID of the VSwitch.
AccessKeyId	String	No	LTAIfCxxxxxxxxxx	The AccessKey ID that Alibaba Cloud issues to a user for service access.
PrivateIpAddress	String	No	172.16.201.69	The private IP address of the read-only instance. It must be within the IP address range provided by the switch. The system automatically assigns an IP address based on the VPCId and VSwitchId by default.
ResourceGroupId	String	No	rg-acfmyxxxxxxxxxx	The ID of the resource group.
DBInstanceStorageType	String	No	local_ssd	The storage type of the instance. Valid values: local_ssd/ephemeral_ssd: local SSDs. cloud_ssd: SSDs. cloud_essd: ESSDs. Note The MySQL database engine supports only local SSDs and the SQL Server database engine supports only SSDs.
Category	String	No	HighAvailability	The edition of the instance. Valid values: Basic HighAvailability AlwaysOn

Response parameters


Parameter	Type	Example	Description
DBInstanceId	String	rr-uf6wjk5xxxxxxx	The ID of the read-only instance.
OrderId	String	10078937xxxxx	The ID of the order.
ConnectionString	String	rr-xxxxx.mysql.rds.aliyuncs.com	The endpoint URL of the read-only instance.
Port	String	3306	The internal port of the read-only instance.
RequestId	String	1E43AAE0-BEE8-43DA-860D-EAF2AA0724DC	The ID of the request.

Examples

Sample requests


http(s)://rds.aliyuncs.com/?Action=CreateReadOnlyDBInstance
&RegionId=cn-hangzhou
&ZoneId=cn-hangzhou-b
&DBInstanceId=rm-uf6wjk5xxxxxxx
&DBInstanceClass=rds.mys2.small
&DBInstanceStorage=20
&EngineVersion=5.6
&PayType=Postpaid
&<Common request parameters>

Successful response examples

XML format

<CreateReadOnlyDBInstanceResponse>
     <OrderId>10078937xxxxx</OrderId>
     <ConnectionString>rm-uf6wjk5xxxxxxx.mysql.rds.aliyuncs.com </ConnectionString>
     <DBInstanceId>rm-uf6wjk5xxxxxxx</DBInstanceId>
     <port>3306</port>
     <RequestId>1E43AAE0-BEE8-43DA-860D-EAF2AA0724DC</RequestId>
</CreateReadOnlyDBInstanceResponse>

JSON format

{
	"Port":"3306",
	"ConnectionString":"rm-uf6wjk5xxxxxxx.mysql.rds.aliyuncs.com",
	"RequestId":"1E43AAE0-BEE8-43DA-860D-EAF2AA0724DC",
	"DBInstanceId":"rm-uf6wjk5xxxxxxx",
	"OrderId":"10078937xxxxx"
}

Error codes


HTTP status code	Error code	Error message	Description
400	InvalidEngineVersion.Malformed	The specified parameter "EngineVersion" is not valid.	The error message returned when the specified EngineVersion parameter is invalid.
400	InvalidSecurityIPList.Malformed	The specified parameter "SecurityIPList" is not valid.	The error message returned when the specified SecurityIPList parameter is invalid.
400	InvalidSecurityIPList.Duplicate	The Security IP address is not in the available range or occupied.	The error message returned when the specified security IP address is in use or is not in the valid range.
400	InvalidParameter	The specified parameter "dbInstanceId" is not valid.	The error message returned when the specified dbInstanceId parameter is invalid.
403	OperationDenied.PrimaryDBInstanceStatus	The operation is not permitted due to status of primary instance.	The error message returned when the status of the master instance does not support this operation. Only the master instance in the running state supports this operation.
400	OperationDenied	VPC IP is in use, please check.	The error message returned when the specified IP address is in use. Change the IP address and try.
404	IncorrectDBInstanceConnType	Current DB instance conn type does not support this operation.	The error message returned when the connection type of the DB instance does not support this operation.
400	InvalidZoneId.NotSupported	The Specified vpc Zone not supported.	The error message returned when the zone does not support the VPC instance. Change the zone and try.

For a list of error codes, visit the API Error Center.