06 - RDS Aurora ElastiCache

RDS Custom

awsrdsrds-customoraclesql-serversaa-c03

RDS Custom for Oracle & Microsoft SQL Server

RDS vs RDS Custom

Feature RDS RDS Custom
OS access No Yes
DB customization No Yes
SSH / SSM access No Yes (SSH or SSM Session Manager)
Supported engines All 7 Oracle & MS SQL Server only
Managed benefits Full Full (setup, operations, scaling)
Internal settings No access Can configure
Patches AWS managed Can install custom patches
Native features No access Can enable

RDS vs RDS Custom

RDSNo OS access, no SSHAll 7 enginesAWS manages patchesNo access to internal settingsRDS CustomOS access via SSH or SSMOracle and MS SQL Server onlyCustom patches allowedNative features can be enabled
RDS Custom trades some AWS control for OS and database access, for Oracle and MS SQL Server only.

Key Points

  • RDS Custom gives you full admin access to the underlying OS and database
  • Supports only Oracle and Microsoft SQL Server
  • You still get all RDS managed benefits (automated setup, operations, scaling)
  • Access via SSH or SSM Session Manager
Before Customizing
  1. Deactivate automation mode — prevents RDS from running maintenance/scaling during your changes
  2. Take a DB snapshot — you may break things since you have OS-level access

Questions & Answers

Q1: What is RDS Custom?

Answer:

A version of RDS that gives you full admin access to the underlying OS and database. Available only for Oracle and Microsoft SQL Server.

Q2: Which database engines support RDS Custom?

Answer:

Only Oracle and Microsoft SQL Server.

Q3: Can you SSH into an RDS Custom instance?

Answer:

Yes. You can access it via SSH or SSM Session Manager. This is the exception to the "no SSH in RDS" rule.

Q4: What should you do before performing customizations on RDS Custom?

Answer:

  1. Deactivate automation mode to prevent RDS from interfering
  2. Take a DB snapshot for recovery in case something breaks
Q5: Do you still get managed benefits with RDS Custom?

Answer:

Yes. You still get automated setup, operations, and scaling — plus the ability to customize the OS and database.

Q6: What can you do with RDS Custom that you can't with regular RDS?

Answer:

  • Configure internal database settings
  • Install custom patches
  • Enable native features
  • Access the underlying EC2 instance
Q7: Why would you choose RDS Custom over regular RDS?

Answer:

When you need OS-level or database-level customization for Oracle or MS SQL Server workloads that require specific patches, native features, or internal configuration changes.

Q8: What is the risk of using RDS Custom?

Answer:

Since you have full OS access, you could potentially break things. Always take a snapshot before making changes.

Q9: Can you use RDS Custom with MySQL or PostgreSQL?

Answer:

No. RDS Custom is only available for Oracle and Microsoft SQL Server.

Q10: How does RDS Custom differ from running a DB on EC2?

Answer:

RDS Custom still provides managed service benefits (automated setup, operations, scaling, backups) while giving you OS access. Running on EC2 means you manage everything yourself.

Check yourself

Quiz

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