DB Instances

A DB Instance is an isolated database environment running in the cloud. A DB Instance can contain multiple user-created databases, and can be accessed using the same tools and applications as a stand-alone database instance.

	Note
	Amazon RDS supports access from any standard SQL client application. Amazon RDS does not allow direct host access via Telnet.

DB Instances are simple to create and modify with the Amazon RDS command line tools, APIs, or the AWS Management Console.

Amazon RDS creates a master user account for your DB Instance as part of the creation process. This master user has permissions to create databases and to perform create, delete, select, update and insert operations on tables the master user creates. You must set the master user password when you create a DB Instance, but you can change it at any time using the Amazon RDS command line tools, APIs, or the AWS Management Console. You can also change the master user password and manage users using standard SQL commands.

For more information on working with DB Instances, go to Creating and Modifying DB Instances.

The DB Instance identifier is a customer-supplied identifier for a DB Instance. This identifier specifies a particular DB Instance when interacting with the Amazon RDS API and commands. The DB Instance identifier must be unique for that customer in an AWS region.

The definition of the term Database Name depends on the database engine in use.

Periodically, the Amazon RDS system performs maintenance on the DB Instance. This maintenance occurs during a user-definable maintenance window, and can include planned MySQL patch roll-outs, as well as implementing pending changes to storage or CPU class for the DB Instance. Maintenance typically requires a short downtime for single-AZ DB Instances.

	Note
	For Multi-AZ deployments, your downtime during system maintenance is limited to the time required for automatic failover to complete. For more information on Multi-AZ deployments, see Multi-AZ Deployments.

If you don't specify a preferred maintenance window when you create the DB Instance, Amazon RDS assigns a 30-minute maintenance window on a randomly selected day of the week.

The 30-minute maintenance window is selected at random from an 8-hour block of time per region. The following table lists the time blocks for each Region from which the default maintenance windows are assigned.

Amazon cloud computing resources are housed in highly available data center facilities. To provide additional scalability and reliability, these data center facilities are located in several different physical locations. These locations are categorized by Regions and Availability Zones.

Regions are large and widely dispersed into separate geographic locations. Availability Zones are distinct locations within a Region that are engineered to be isolated from failures in other Availability Zones and provide inexpensive, low latency network connectivity to other Availability Zones in the same Region.

Important

Each Region is completely independent. Any Amazon RDS activity you initiate (e.g. creating database instances or listing available database instances) runs only in your current default Region. The default Region can be changed by setting the EC2_REGION environment variable, or be overridden by using the --url parameter with the command line interface. See Common Options for API Tools for more information.

To create or work with an Amazon RDS DB Instance in a specific Region, use the corresponding regional service endpoint.

Amazon RDS supports the endpoints listed in the following table.

If you do not explicitly specify an endpoint, the US-East (Northern Virginia) Region endpoint is the default.

You can run your DB Instance as a Multi-AZ deployment. When you select this option, Amazon automatically provisions and maintains a synchronous standby replica in a different Availability Zone. The primary DB Instance is synchronously replicated across Availability Zones to the standby replica to provide data redundancy, eliminate I/O freezes during system backups, enhance availability during planned system maintenance, and help protect your databases against DB Instance failure and Availability Zone disruption.

	Note
	Multi-AZ deployments are currently only supported with the MySQL database engine.

In the event of a planned or unplanned outage of your primary DB Instance, Amazon RDS automatically switches to the standby replica. The automatic failover mechanism simply changes the canonical name record (CNAME) of the main DB Instance to point to the standby DB Instance.

Amazon RDS handles the failover automatically so you can resume database operations as quickly as possible without administrative intervention. The primary DB Instance switches over automatically to the standby replica if any of the following conditions occur:

You can create a Multi-AZ deployment by simply specifying the Multi-AZ option when creating a DB Instance. You can convert existing DB Instances to Multi-AZ deployments by modifying the DB Instance and specifying the Multi-AZ option.

Multi-AZ deployments are not a scaling solution for reads and do not allow you to use the standby replica to serve read traffic.

The Amazon RDS Read Replica feature lets you create a DB Instance as a replica of another DB Instance. Any updates to the data on the source DB Instance are replicated to the Read Replica DB Instances using the built-in replication feature of MySQL. You can use the Read Replica feature to scale beyond the capacity constraints of a single DB Instance for read-heavy database workloads.

	Note
	The Amazon RDS Read Replica feature is currently only supported with the MySQL database engine. The Amazon RDS Read Replica feature is not supported for DB Instances running in an Amazon Virtual Private Cloud (VPC).

Using the Read Replica feature is easy; simply create a Read Replica DB Instance using AWS Management Console or the new CreateDBInstanceReadReplica API or rds-create-db-instance-read-replica command line tool and specify the source DB Instance that you want to replicate. You can create up to five Read Replicas per DB Instance.

When you initiate the creation of a Read Replica, Amazon RDS takes a snapshot of the source DB Instance and begins replication. As a result, you will experience a brief I/O suspension on your source DB Instance as the snapshot occurs (this I/O suspension is mitigated if the source DB Instance is a Multi-AZ deployment, because snapshots are taken from the Multi-AZ standby).

You can use the standard DescribeDBInstances API or the rds-describe-db-instances command line tool to return a list of all the DB Instances you have deployed (including Read Replicas), or click the DB Instances tab of the Amazon RDS Management Console.

Unlike Multi-AZ deployments, updates are applied to Read Replica DB Instances using asynchronous replication, and are subject to replication lag.

Due to replication lag, recent database updates made to a source DB Instance might not be present on associated Read Replicas in the event of an unplanned outage on the source DB Instance; because of this, Read Replicas are not intended to protect against DB Instance or Availability Zone failure.

	Note
	Replication lag can be monitored as a CloudWatch metric. For more information on monitoring, see DB Instance Monitoring.

You can set a Multi-AZ deployment as the source DB Instance for your Read Replicas) to combine the availability and durability benefits of Multi-AZ with the scaling benefits of Read Replicas.

You can simply delete Read Replica DB Instances when you no longer need them.

	Note
	A Read Replica will stay active and continue accepting read traffic even after its corresponding source DB Instance has been deleted. You must explicitly delete the Read Replica DB Instance.

Reserved DB Instances let you make a one-time up-front payment for a DB Instance and reserve the DB Instance for a one- or three-year term at significantly lower rates.

Reserved Instances are available in three varieties—Heavy Utilization, Medium Utilization, and Light Utilization—that enable you to optimize your Amazon RDS costs based on your expected utilization.

You can use the command line tools, the API, or the AWS Management Console to list and purchase available Reserved DB Instance offerings. The three types of Reserved DB Instance offerings are based on DB instance class, duration, and whether or not the Reserved DB instance is Single-AZ or Multi-AZ.