After an upgrade done a while ago (from 11g to 12c), how do I ENSURE that the 11g binaries aren't be

After an database upgrade done months ago (from 11g to 12c), how do I ENSURE that the 11g binaries aren't being used anywhere on the RHEL 6 database server by any of the processes or scripts?

Relatively new to this job at this site so not 100% sure what may have been done.

I've recursively GREP'd the files on the database server looking for any hard coded 11g reference issues.   I only find in redo logs, but no where else.   

Doing a "strings" on the redo*log file shows:

[oracle@MLDBANDB DEV]$ strings redo_06b.log | grep "11.2.0."

11.2.0.4

11.2.0.4.0

*A$11.2.0.4

*A$11.2.0.4.0

*A$11.2.0.4

*A$11.2.0.4.0

Might consider renaming the 11g binaries dirs on development db server to see what arises.