Hi @arebbeadle ,

Both of these users are oracle users/owners and utilized by oracle for specific functionalities. 

According to oracle documentation: 

17.1.1 CTXSYS User

The CTXSYS user is created during installation and can:

• View all indexes

• Sync all indexes

• Run ctxkbtc, the knowledge base extension compiler

• Query all system-defined views

• Perform all tasks of a user with the CTXAPP role

MDSYS owns  Oracle Spatial objects. You can read more about these objects in this doc. Also refer this document for changes in oracle 19C for  Oracle Spatial objects and MDSYS. 

Hope this helps!

Thanks,

Kasun

Thank you,