Turning on extended data types in RDS for Oracle - Amazon Relational Database Service
Considerations for extended data typesTurning on extended data types for a new DB instanceTurning on extended data types for an existing DB instance

Turning on extended data types in RDS for Oracle

Amazon RDS for Oracle supports extended data types. With extended data types, the maximum size is 32,767 bytes for the VARCHAR2, NVARCHAR2, and RAW data types. To use extended data types, set the MAX_STRING_SIZE parameter to EXTENDED. For more information, see Extended data types in the Oracle documentation.

If you don't want to use extended data types, keep the MAX_STRING_SIZE parameter set to STANDARD (the default). In this case, the size limits are 4,000 bytes for the VARCHAR2 and NVARCHAR2 data types, and 2,000 bytes for the RAW data type.

You can turn on extended data types on a new or existing DB instance. For new DB instances, DB instance creation time is typically longer when you turn on extended data types. For existing DB instances, the DB instance is unavailable during the conversion process.

Considerations for extended data types

Consider the following when you enable extended data types for your DB instance:

  • When you turn on extended data types for a new or existing DB instance, you must reboot the instance for the change to take effect.

  • After you turn on extended data types, you can't change the DB instance back to use the standard size for data types. If you set the MAX_STRING_SIZE parameter back to STANDARD it results in the incompatible-parameters status.

  • When you restore a DB instance that uses extended data types, you must specify a parameter group with the MAX_STRING_SIZE parameter set to EXTENDED. During restore, if you specify the default parameter group or any other parameter group with MAX_STRING_SIZE set to STANDARD it results in the incompatible-parameters status.

  • When the DB instance status is incompatible-parameters because of the MAX_STRING_SIZE setting, the DB instance remains unavailable until you set the MAX_STRING_SIZE parameter to EXTENDED and reboot the DB instance.

Turning on extended data types for a new DB instance

When you create a DB instance with MAX_STRING_SIZE set to EXTENDED, the instance shows MAX_STRING_SIZE set to the default STANDARD. Reboot the instance to enable the change.

To turn on extended data types for a new DB instance

  1. Set the MAX_STRING_SIZE parameter to EXTENDED in a parameter group.

    To set the parameter, you can either create a new parameter group or modify an existing parameter group.

    For more information, see Parameter groups for Amazon RDS.

  2. Create a new RDS for Oracle DB instance.

    For more information, see Creating an Amazon RDS DB instance.

  3. Associate the parameter group with MAX_STRING_SIZE set to EXTENDED with the DB instance.

    For more information, see Creating an Amazon RDS DB instance.

  4. Reboot the DB instance for the parameter change to take effect.

    For more information, see Rebooting a DB instance.

Turning on extended data types for an existing DB instance

When you modify a DB instance to turn on extended data types, RDS converts the data in the database to use the extended sizes. The conversion and downtime occur when you next reboot the database after the parameter change. The DB instance is unavailable during the conversion.

The amount of time it takes to convert the data depends on the DB instance class, the database size, and the time of the last DB snapshot. To reduce downtime, consider taking a snapshot immediately before rebooting. This shortens the time of the backup that occurs during the conversion workflow.

Note

After you turn on extended data types, you can't perform a point-in-time restore to a time during the conversion. You can restore to the time immediately before the conversion or after the conversion.

To turn on extended data types for an existing DB instance

  1. Take a snapshot of the database.

    If there are invalid objects in the database, Amazon RDS tries to recompile them. The conversion to extended data types can fail if Amazon RDS can't recompile an invalid object. The snapshot enables you to restore the database if there is a problem with the conversion. Always check for invalid objects before conversion and fix or drop those invalid objects. For production databases, we recommend testing the conversion process on a copy of your DB instance first.

    For more information, see Creating a DB snapshot for a Single-AZ DB instance for Amazon RDS.

  2. Set the MAX_STRING_SIZE parameter to EXTENDED in a parameter group.

    To set the parameter, you can either create a new parameter group or modify an existing parameter group.

    For more information, see Parameter groups for Amazon RDS.

  3. Modify the DB instance to associate it with the parameter group with MAX_STRING_SIZE set to EXTENDED.

    For more information, see Modifying an Amazon RDS DB instance.

  4. Reboot the DB instance for the parameter change to take effect.

    For more information, see Rebooting a DB instance.