Underlying Implementation of VARCHAR data types

I recently inherited management of several Oracle databases. By background I am not an Oracle DBA, but have over a decade of experience using other RDBMSs such as Informix and DB2. Eager to learn new Oracle skills I started taking inventory of the databases. One of the outstanding things that caught my eye was the use of VARCHAR for all of the character based data fields. Not a single fixed CHAR field to be found. When I asked around, the developers told me, that's the way you do it in Oracle.

In my DB2 databases, there are considerations with both storage and performance when choosing VARCHAR over CHAR. There is a 4-byte overhead for each row (2 for the data page offset and 2 for the length). I am curious to understand the underlying implementation on the Oracle side. What overhead is incurred (if any) for VARCHAR? And are there any similar performance considerations (regarding querying, updating and indexing)?

The limited docs that I have don't mention anything about this area. I'm anxious to come up to speed with my newly inherited environment.

Thanks,
Mike Received on Fri Mar 05 2004 - 16:26:56 CST