Introduction to Cloning Oracle RAC

Cloning is the process of copying an existing Oracle RAC installation to a different location and updating the copied bits to work in the new environment. The changes made by one-off patches applied on the source Oracle home, would also be present after the clone operation. The source and the destination path (host to be cloned) need not be the same.

Some situations in which cloning is useful are:

  • Cloning provides a way to prepare an Oracle home once and deploy it to many hosts simultaneously. You can complete the installation silently, as a noninteractive process. You do not need to use a graphical user interface (GUI) console and you can perform cloning from a Secure Shell (SSH) terminal session, if required.

  • Cloning enables you to create an installation (copy of a production, test, or development installation) with all patches applied to it in a single step. Once you have performed the base installation and applied all patch sets and patches on the source system, the clone performs all of these individual steps as a single procedure. This is in contrast to going through the installation process to perform the separate steps to install, configure, and patch the installation on each node in the cluster.

  • Installing Oracle RAC by cloning is a very quick process. For example, cloning an Oracle home to a new cluster of more than two nodes requires a few minutes to install the Oracle base software, plus a few minutes more for each node (approximately the amount of time it takes to run the root.sh script).

The cloned installation behaves the same as the source installation. For example, the cloned Oracle home can be removed using Oracle Universal Installer or patched using OPatch. You can also use the cloned Oracle home as the source for another cloning operation. You can create a cloned copy of a test, development, or production installation by using the command-line cloning scripts. The default cloning procedure is adequate for most usage cases. However, you can also customize various aspects of cloning, for example, to specify custom port assignments, or to preserve custom settings.

The cloning process works by copying all of the files from the source Oracle home to the destination Oracle home. Thus, any files used by the source instance that are located outside the source Oracle home's directory structure are not copied to the destination location.

The size of the binaries at the source and the destination may differ because these are relinked as part of the clone operation and the operating system patch levels may also differ between these two locations. Additionally, the number of files in the cloned home would increase because several files copied from the source, specifically those being instantiated, are backed up as part of the clone operation.