Quotas and constraints for Amazon RDS

Following, you can find a description of the resource quotas and naming constraints for Amazon RDS.

Quotas in Amazon RDS

Each AWS account has quotas, for each AWS Region, on the number of Amazon RDS resources that can be created. After a quota for a resource has been reached, additional calls to create that resource fail with an exception.

The following table lists the resources and their quotas per AWS Region.

Resource	Default quota
Authorizations per DB security group	20
Burst balance for instances <1 tebibyte (TiB)	3000 IOPS
Concurrent DB snapshot export tasks	5
Cross-Region DB snapshot copy requests	5
DB instances	40
DB security groups	25
DB subnet groups	50
Event subscriptions	20
IAM roles per DB instance	5
Manual DB snapshots	100
Option groups	20
Parameter groups	50
Proxies	20
Read replicas per primary	5
Reserved DB instances	40
Rules per security group	20
Rules per virtual private cloud (VPC) security group	50 inbound, 50 outbound
Subnets per subnet group	20
Tags per resource	50
Total storage for all DB instances	100 terabytes (TB)
VPC security groups	5

Note

By default, you can have up to a total of 40 DB instances. RDS DB instances, Aurora DB instances, Amazon Neptune instances, and Amazon DocumentDB instances apply to this quota.

The following limitations apply to the Amazon RDS DB instances:

• 10 for each SQL Server edition (Enterprise, Standard, Web, and Express) under the "license-included" model

• 10 for Oracle under the "license-included" model

• 40 for MySQL, MariaDB, or PostgreSQL

• 40 for Oracle under the "bring-your-own-license" (BYOL) licensing model

If your application requires more DB instances, you can request additional DB instances by opening the Service Quotas console. In the navigation pane, choose AWS services. Choose Amazon Relational Database Service (Amazon RDS), choose a quota, and follow the directions to request a quota increase. For more information, see Requesting a quota increase in the Service Quotas User Guide.

Backups managed by AWS Backup are considered manual DB snapshots, but don't count toward the manual snapshot quota. For information about AWS Backup, see the AWS Backup Developer Guide.

Naming constraints in Amazon RDS

The following table describes naming constraints in Amazon RDS.

Resource or item	Constraints
DB instance identifier	Identifiers have these naming constraints: Must contain 1–63 alphanumeric characters or hyphens. First character must be a letter. Can't end with a hyphen or contain two consecutive hyphens. Must be unique for all DB instances per AWS account, per AWS Region.
Database name	Database name constraints differ for each database engine . For more information, see the available settings when creating each DB instance. Note This approach doesn't apply to SQL Server. For SQL Server, you create your databases after you create your DB instance.
Master user name	Master user name constraints differ for each database engine. For more information, see the available settings when creating each DB instance.
Master password	The password for the database master user can include any printable ASCII character except /, ", @, or a space. Master password length constraints differ for each database engine. For more information, see the available settings when creating each DB instance.
DB parameter group name	These names have these constraints: Must contain 1–255 alphanumeric characters. First character must be a letter. Hyphens are allowed, but the name cannot end with a hyphen or contain two consecutive hyphens.
DB subnet group name	These names have these constraints: Must contain 1–255 characters. Alphanumeric characters, spaces, hyphens, underscores, and periods are allowed.

Maximum number of database connections

The maximum number of simultaneous database connections varies by the DB engine type and the memory allocation for the DB instance class. The maximum number of connections is set in the parameter group associated with the DB instance, except for Microsoft SQL Server, where it is set in the server properties for the DB instance in SQL Server Management Studio (SSMS).

DBInstanceClassMemory is in bytes. You can find the value of DBInstanceClassMemory in gibibytes (GiB) in the table of Hardware specifications for DB instance classes .

Note

For Oracle, you set the maximum number of user processes and user and system sessions.

Maximum database connections
DB engine	Parameter	Allowed values	Default value	Description
MariaDB and MySQL	max_connections	1–100000	{DBInstanceClassMemory/12582880}	Number of simultaneous client connections allowed
Oracle	processes	80–20000	LEAST({DBInstanceClassMemory/9868951}, 20000)	User processes
	sessions	100–65535	–	User and system sessions
PostgreSQL	max_connections	6–8388607	LEAST({DBInstanceClassMemory/9531392}, 5000)	Maximum number of concurrent connections
SQL Server	Maximum number of concurrent connections	0–32767	0 (unlimited)	Maximum number of concurrent connections

The following example shows how to calculate max_connections for a MariaDB or MySQL DB instance using the db.m5.xlarge instance class. DBInstanceClassMemory is 16 GiB, or 17,179,869,184 bytes. That divided by 12,582,880 = 1365 connections maximum.

For MariaDB and MySQL DB instances, setting the max_connections parameter to a large value might cause a DB instance to be placed in the incompatible-parameters status. For more information, see Diagnosing and resolving incompatible parameters status for a memory limit.

Note

You might see fewer than the maximum number of DB connections. This is to avoid potential out-of-memory issues.

File size limits in Amazon RDS

File size limits apply to certain Amazon RDS DB instances. For more information, see the following engine-specific limits:

• MariaDB file size limits in Amazon RDS

• MySQL file size limits in Amazon RDS

• Oracle file size limits in Amazon RDS