This might be quite trivial for most ODI developers but key for ODI newbies.
It is a best practice to use a separate schema for holding ODI temporary objects (such as C$_ or I$ tables).
This schema is named “WORK SCHEMA” in ODI and it can be setup in the “Physical Schema” within the Topology tab. For instance, “ODI_TEMP” is a quite intuitive name for this purpose:
For more information on this topic, please refer to: http://odiexperts.com/why-creating-a-separate-schema-for-temporary-tables-in-odi/