Discovering and analyzing migration limitations with Amazon DMS Fleet Advisor - Amazon Database Migration Service
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Discovering and analyzing migration limitations with Amazon DMS Fleet Advisor

You can use the DMS data collector to discover database features that your target engine doesn't support. To choose the right migration target, you should consider these limitations.

The DMS data collector discovers specific source database features. Then, DMS Fleet Advisor analyses source features from a migration standpoint to the specified target and provides additional information about the limitation and includes recommended actions to address or avoid this limitation. Also, DMS Fleet Advisor calculates the impact of these limitations.

The list of limitations is available in the Target engine details page. Navigate to this page from the Recommendations page in the left navigation menu. From the list of targets, choose the target engine to examine. The list of limitations is at the bottom of the page.

The following table includes MySQL database features that Amazon RDS for MySQL doesn't support.

Limitation Description Impact

Authentication plugins

Amazon RDS doesn't support MySQL authentication plugins.

Low

Error logging to the system log

Amazon RDS doesn't support writing the error log to the system log.

Low

Global transaction identifiers

You can use global transaction identifiers with all RDS for MySQL 5.7 versions, and RDS for MySQL version 8.0.26 and higher MySQL 8.0 versions.

Low

Group Replication

Amazon RDS doesn't support the MySQL Group Replication plugin.

Low

InnoDB tablespace encryption

Amazon RDS doesn't support the InnoDB tablespace encryption.

Low

InnoDB reserved word

InnoDB is a reserved word for Amazon RDS for MySQL. You can't use this name for a MySQL database.

Low

Keyring plugin

Amazon RDS doesn't support the MySQL keyring plugin.

Low

Password validation plugin

Amazon RDS doesn't support the MySQL validate_password plugin.

Low

Persisted system variables

Amazon RDS doesn't support MySQL persisted system variables.

Low

Restricted access

Amazon RDS restricts access to certain system procedures and tables that require advanced permissions. Also, Amazon RDS doesn't allow direct host access to a DB instance by using Telnet, Secure Shell (SSH), or Windows Remote Desktop Connection.

Low

Rewriter query rewrite plugin

Amazon RDS doesn't support the MySQL Rewriter query rewrite plugin.

Low

Semisynchronous replication

Amazon RDS doesn't support the MySQL semisynchronous replication.

Low

Transportable Tablespaces

Amazon RDS doesn't support the MySQL Transportable Tablespaces feature.

Low

X Plugin

Amazon RDS doesn't support the MySQL X Plugin.

Low

The following table includes Oracle database features that Amazon RDS for Oracle doesn't support.

Limitation Description Impact

Active Data Guard

You can't use Active Data Guard with Oracle multitenant container databases (CDB).

Medium

Automatic Storage Management

Amazon RDS doesn't support Oracle Automatic Storage Management (Oracle ASM).

Medium

Database Activity Streams

Amazon RDS doesn't support Oracle Database Activity Streams for the single-tenant architecture.

High

File size limit

The maximum size of a single file on RDS for Oracle DB instances is 16 TiB.

Medium

FTP and SFTP

Amazon RDS doesn't support FTP and SFTP.

Medium

Hybrid partitioned tables

Amazon RDS doesn't support Oracle hybrid partitioned tables.

High

Oracle Data Guard

Amazon RDS doesn't Oracle Data Guard for the single-tenant architecture.

High

Oracle Database Vault

Amazon RDS doesn't support Oracle Database Vault.

High

Oracle DBA privileges Vault

Amazon RDS has limitations for Oracle DBA privileges. For more information, see Limitations for Oracle DBA privileges.

High

Oracle Enterprise Manager

Amazon RDS doesn't Oracle Enterprise Manager for the single-tenant architecture.

High

Oracle Enterprise Manager Agent

Amazon RDS doesn't Oracle Enterprise Manager Agent for the single-tenant architecture.

Medium

Oracle Enterprise Manager Cloud Control Management Repository

You can't use an Amazon RDS for Oracle DB instance for Oracle Enterprise Manager Cloud Control Management Repository.

High

Oracle Flashback Database

Amazon RDS doesn't support the Oracle Flashback Database feature.

High

Oracle Label Security

Amazon RDS doesn't support Oracle Label Security for the single-tenant architecture. You can use Oracle Label Security only with multitenant container databases (Oracle CDB).

High

Oracle Messaging Gateway

Amazon RDS doesn't support Oracle Messaging Gateway.

High

Oracle Real Application Clusters

Amazon RDS doesn't support Oracle Real Application Clusters (Oracle RAC).

High

Oracle Real Application Testing

Amazon RDS doesn't support Oracle Real Application Testing.

High

Oracle Snapshot Standby databases

Amazon RDS doesn't support Oracle Snapshot Standby databases.

High

Public synonyms

Amazon RDS doesn't support public synonyms for Oracle-supplied schemas.

Medium

Schemas for unsupported features

Amazon RDS doesn't support schemas for Oracle features and components that require system privileges.

High

Pure unified auditing

Amazon RDS doesn't support the pure unified auditing. You can use the unified auditing in mixed mode.

Medium

Workspace Manager

Amazon RDS doesn't support the Oracle Database Workspace Manager WMSYS schema.

High

The following table includes PostgreSQL database features that Amazon RDS for PostgreSQL doesn't support.

Limitation Description Impact

Concurrent connections

The maximum number of concurrent connections to your RDS for PostgreSQL instance is limited by the max_connections parameter.

Low

Newest versions

Amazon RDS doesn't apply major version upgrades automatically. To perform a major version upgrade, modify your DB instance manually. For more information, see Choosing a major version upgrade for PostgreSQL.

Low

Reserved connections

Amazon RDS reserves up to 3 connections for system maintenance. If you specify a value for the user connections parameter, add 3 to the number of connections that you expect to use.

Low

Supported extensions

RDS for PostgreSQL supports a limited number of extensions for the PostgreSQL database engine. You can find a list of supported extensions in the default DB parameter group for your PostgreSQL version. You can also see the current extensions list using psql by showing the rds.extensions parameter.

Low

Tablespace splitting or isolation

You can't use tablespaces for I/O splitting or isolation. In RDS for PostgreSQL, all storage is on a single logical volume.

Low

The following table includes SQL Server database features that Amazon RDS for SQL Server doesn't support.

Limitation Description Impact

Backing up to Microsoft Azure Blob Storage

RDS for SQL Server doesn't support backing up to Microsoft Azure Blob Storage.

Medium

Buffer pool extension

RDS for SQL Server doesn't support the buffer pool extension.

High

Custom password policies

RDS for SQL Server doesn't support custom password policies.

Medium

Data Quality Services

RDS for SQL Server doesn't support SQL Server Data Quality Services (DQS).

High

Database Log Shipping

RDS for SQL Server doesn't support database Log Shipping.

High

Database names

Database names have the following limitations: can't start with rdsadmin; can't start or end with a space or a tab; can't contain any of the characters that create a new line; can't contain a single quotation mark (').

Medium

Database snapshots

RDS for SQL Server doesn't support database snapshots. You can use only DB instance snapshots in Amazon RDS.

Medium

Extended stored procedures

RDS for SQL Server doesn't support extended stored procedures, including xp_cmdshell.

High

File tables

RDS for SQL Server doesn't support file tables.

Medium

FILESTREAM support

RDS for SQL Server doesn't provide FILESTREAM support.

Medium

Linked servers

RDS for SQL Server provides limited support for linked servers.

High

Machine Learning and R Services

RDS for SQL Server doesn't support Machine Learning and R Services because you need OS access to install these services.

High

Maintenance plans

RDS for SQL Server doesn't support maintenance plans.

High

Performance Data Collector

RDS for SQL Server doesn't support Performance Data Collector.

High

Policy-Based Management

RDS for SQL Server doesn't support Policy-Based Management.

Medium

PolyBase

RDS for SQL Server doesn't support PolyBase.

High

Replication

RDS for SQL Server doesn't support replication.

Medium

Resource Governor

RDS for SQL Server doesn't support Resource Governor.

High

Server-level triggers

RDS for SQL Server doesn't support server-level triggers.

Medium

Service Broker endpoints

RDS for SQL Server doesn't support Service Broker endpoints.

High

SSAS

Consider the limitations that apply to running SQL Server Analysis Services (SSAS) on RDS for SQL Server. For more information, see Limitations.

Low

SSIS

Consider the limitations that apply to running SQL Server Integration Services (SSIS) on RDS for SQL Server. For more information, see Limitations.

Low

SSRS

Consider the limitations that apply to running SQL Server Reporting Services (SSRS) on RDS for SQL Server. For more information, see Limitations.

Low

Storage size for SQL Server DB instances

The maximum storage size for SQL Server General Purpose (SSD) storage and Provisioned IOPS storage instances is 16 TiB.

The maximum storage size for SQL Server Magnetic storage instances is 1 TiB.

High

Stretch Database

RDS for SQL Server doesn't support the SQL Server Stretch Database feature.

Medium

T-SQL endpoints

RDS for SQL Server doesn't support all operations that use CREATE ENDPOINT.

High

TRUSTWORTHY database property

RDS for SQL Server doesn't support the TRUSTWORTHY database property because it requires the sysadmin role.

Medium

The following table includes a list of recommendation issues. DMS Fleet Advisor analyses source and target database features and provides these migration limitations. The limitation with Blocker impact means that DMS Fleet Advisor can't generate target recommendations for the source database.

Limitation Description Impact

Appropriate instance is not found

Amazon DMS can't find a target instance that can work as a right-sized migration destination for a combination of your source database metrics.

Blocker

Appropriate instance is not found by IOPS

The source database uses a number of IOPS, which exceeds the maximum number of IOPS for the possible target DB instances.

Blocker

Appropriate instance is not found by RAM

The source database uses a number of GB of RAM, which exceeds the maximum size of RAM for the possible target DB instances.

Blocker

Appropriate instance is not found by storage size

The source database uses a number of TB of storage, which exceeds the maximum storage size for the possible target DB instances.

Blocker

Appropriate instance is not found by edition

The source database has an edition, which is not supported by Amazon RDS.

Blocker

Appropriate instance is not found by CPU cores

The source database has a number of CPU cores, which exceeds the maximum number of CPU cores for the possible target DB instances.

Blocker

Appropriate instance is not found by version

Your source database has version, which Amazon DMS doesn’t recognize.

Blocker

CPU parameter is undefined

The DMS data collector didn't collect information about the CPU that your source database uses. Make sure that you collected the required metrics and configured credentials for data forwarding in your data collector. See Configuring credentials for data forwarding.

Blocker

Memory parameter is undefined

The DMS data collector didn't collect information about the memory that your source database uses. Make sure that you collected the required metrics and configured credentials for data forwarding in your data collector. See Configuring credentials for data forwarding.

Blocker

Storage size parameter is undefined

The DMS data collector didn't collect information about the storage size that your source database uses. Make sure that you collected the required metrics and configured credentials for data forwarding in your data collector. See Configuring credentials for data forwarding.

Blocker

Storage IOPS parameter is undefined

The DMS data collector didn't collect the storage IOPS metrics for your source database uses. Make sure that you collected the required metrics and configured credentials for data forwarding in your data collector.

Blocker

Not Enough Data

The DMS data collector didn't collect enough data to generate a target recommendation. Make sure that you configured credentials for data forwarding in your data collector. See Configuring credentials for data forwarding.

Blocker

Database edition is undefined

 The DMS data collector didn't collect information about your source database edition. Make sure that you collected the required metrics and configured credentials for data forwarding in your data collector. See Configuring credentials for data forwarding.

Blocker

Unknown Error

DMS Fleet Advisor can't generate target recommendations for your source database.

Blocker

Database version is undefined

 The DMS Fleet Advisor didn't collect information about your source database version. DMS Fleet Advisor recommends that you use the latest database version for your source database. If you choose this recommendation, then you must upgrade your database version. Review the generated target recommendations for your source database and make sure that these recommendations meet your requirements.

High

Increase the number of database connections in RDS settings

 Your source database requires certain number of connections. By default, the number of available connections for Amazon RDS database instances is different. Make sure that you change this default value when you create your RDS database instance. To do so, update the max_connections parameter value in Parameter Groups.

Medium

Target edition is compatible

 The target recommendation for your source database uses a different database edition. Your source database edition supports the same features as the recommended target edition. However, choosing this new database edition might increase your expenses.

Medium

Storage throughput parameter is undefined

 The DMS data collector didn't collect the storage throughput metrics for your source database uses. Review the generated target recommendations for your source database and make sure that these recommendations meet your requirements.

Medium

Database connection number parameter is undefined

The DMS data collector didn't collect information about the number of connections that your source database uses. Review the generated target recommendations for your source database and make sure that these recommendations meet your requirements. Alternatively, request a quota increase.

Medium

Database downgrade version

Your source database runs on a higher version than the Amazon RDS database. To downgrade your database version, make sure that you don't use the features that aren't implemented in lower version. Alternatively, use Amazon EC2 as a migration target.

Medium

Target edition is different

 The target recommendation for your source database uses a different database edition. Your source database edition is compatible with the recommended target edition. However, the recommended target database edition doesn't support some features of your source database edition. Choosing this new database edition might increase your expenses.

Medium

Upgrade from an unsupported version

 Your source database has reached the end of support stage. To use the latest DB engine version as a target, upgrade your database before the migration. Alternatively, use Amazon EC2 as a migration target.

Depending on the database engine, use one of the following links for Learn more:

Upgrading MySQL

Upgrade SQL Server

Upgrade OracleDB

Upgrade PostgreSQL

Medium