We have client applications data stored in (multiple) Oracle DB. Client want to migrate the content from all DBs to Oracle UCM. Can someone please help me how to migrate and what all things I should check/be ready with to perform above migration?
You can search this forum for threads about migration (there were quite a few from various environment).
In a nutshell, while migrating from any content repository to UCM, you always need to get two things from the source, metadata and the content, and somehow map it to metadata and content in UCM (destination). Apparently, if you have multiple sources, the metadata model might be different in each of them. Therefore, you will need to find an agreement with your customer how to map them. The process of migration itself is, then, relatively easy - you can use BatchLoader or write a loader of your own (e.g. using RIDC or WebServices).
In the forum there are also few companies offering their services.
To migrate content to UCM you need a set of metadata and a set of files (the metadata should include (relative) paths to the files).
To add content to UCM you can create a hda file containing sets of parameters for service calls to UCM. To create this file you can manually add parameters for each file or you can generate this file based on data from a table. If you already have document metadata in some tables all the better (otherwise you can use SQL loader to load data from files into database tables). You can then use PL/SQL to generate your hda files using the UTL_FILE package.
The great thing about PLSQL package for this is that you can also automate any transformations that may need to take place (converting metadata fields from one system to matching UCM metadata fields; ie. document types). Also, if you give each record in your "migration" table a unique id, you can add this metadata in the call to UCM (first make a UCM field like xMigrationID) and you can use this for automated validations.
There are endless possibilities but ofcourse you must always take into account the attributes of your migration (it's not smart to do all the above if you want to migrate 100 documents). If you want to migrate millions of documents to a production environment and still want to be able to validate if each document is correctly migrated, the overhead of building some custom PLSQL seems a lot smaller.
Proventeq has got a product, "the Migration Accelerator", that can easily migrate Content stored in Content DB to Oracle UCM. This is our website: www.proventeq.com. Get in touch if you want to discuss or want to see a demo.