Express Edition is a nice starter database which comes for free and does not need a license. Well, you do not get support for it either. There where XE databases in 10g and in 11g, but in this blog post I look into current XE which is 18c. I will concentrate on how to get the most out of it. This mainly goes to its space limitation. After discussion with clients and other consultants often there comes the concern of limited space, which is documented to be 12 GB in 18c. So the question here is how to install an XE as lightweight as possible without any unneeded overhead. And how to store the real user data as compact as possible.
After installation of XE 18c and following the default deployment you will have a CDB with one PDB. This is what is called by the “/etc/init.d/oracle-xe-18c configure” under the hood:
The registry components are visible here twice as it is loaded into CDB$ROOT and PDB XEPDB1. Actually it is also there a third time – in PDB$SEED. This PDB is excluded from the most CDB_-views by default and so missing in the output above. So having OLAP, Multimedia and so on in this CDB multiple times seems not to be that lightweight any more. We waste space for probably unneeded components.