Zero Downtime Migration

When you need to migrate into OCI we have a cool – and free – tool that you can use: Zero Downtime Migration (ZDM). In short: ZDM builds a standby database in OCI and when you are ready to migrate, all it takes is a simple switch-over. My fellow Product Manager, Ricardo Gonzalez, has made a good video that gives you a perfect introduction in less than two minutes.

In this blog post series I will take you through the entire process using version 19.2 (the latest at time of writing). In the end you will know all there is to know – and you can start migrating your databases into OCI. Granted, in this first blog post there will be a lot of text but I want you to have all the details. Take a deep breath – here we go!

You can use Zero Downtime Migration to easily migrate to Oracle Cloud Infrastructure - OCI

Platforms

Your source database can be located on-premises, in OCI Classic (you know, our old cloud) or already in OCI. The latter scenario is useful when you want to migrate between regions or locations or between system types (like from Virtual Machine to Bare Metal).

The operating system must be Linux. No other platforms are supported. And you can migrate into one of these platforms:

  • Virtual Machine DB System
  • Bare Metal DB System
  • Exadata DB System
  • Exadata Cloud at Customer

Release And Edition

You can use ZDM if the database is 11.2.0.4 or newer and the target release will be the same. If you need to migrate into a newer database release, you must manually upgrade the database afterwards, or use another approach. However, it is possible to migrate to a higher patch level. You just have to manually execute datapatch afterwards.

If your source database is Enterprise Edition the database will be migrated with zero downtime. For Standard Edition the source database will be offline during the entire migration. The reason is that Data Guard is used behind the scenes, and it is not licensed on Standard Edition.

Last, you can’t migrate between editions, e.g. from Standard Edition to Enterprise Edition.

Architecture

Your source database can be non-CDB or CDB.

  • Non-CDB databases will be migrated to non-CDB. In a future release of ZDM we plan to include PDB conversion as well.
  • CDBs will be migrated as-is -meaning with all PDBs.

Your source database can be single instance, RAC One Node or RAC.

  • Single instance databases are migrated to single instance or, optionally, to a RAC database.
  • RAC One Node and RAC databases are always migrated into a RAC database.

Encryption

Your source database can be encrypted, but it is not required. Unencrypted databases will be encrypted on-the-fly once they are created in OCI. The initial backup of the source database is sent over an encrypted connection to OCI Object Storage, and redo are transferred over encrypted SQL*Net.

Be aware, for unencrypted databases (or in fact databases that are not licensed for Advanced Security Option) you are not allowed to fallback to the source environment after the switch-over. The target environment will be encrypted using TDE Tablespace Encryption, and, thus, the redo will be encrypted. To decrypt the redo at the source environment – you need a license for Advanced Security Option.

Network Connectivity

  • The ZDM service host needs SSH access (22) to both the source and target database host.
  • The source and target database host needs access to OCI Object Storage over HTTPS (443).
  • SQL*Net connection (1521) are needed between the two databases hosts. In fact, you only need connection from the target database host and back to the source, if you want the option of being able to fallback to the source database host after the switch-over.

References

In case you want to read more here are some useful links:

Other Blog Posts In This Series

This is the introduction blog post in this series. Over the next days the other blog posts will follow. Stay tuned!

2 thoughts on “Zero Downtime Migration

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s