RMAN duplicate from backup location fails with RMAN-05579 on Windows. Turns out, RMAN on Windows requires UNC paths rather than mapped drive letters for network shares.
EM Express calls WRI$_REPT_SQLPI, generating a SQL statement with a cartesian join involving DBA_ADVISOR_OBJECTS, which can use 100% CPU for hours.
SQL*Plus 12.2 ignores %SQLPATH%\LOGIN.SQL
Enabling OS authentication for Oracle databases running on Windows prevents password authenticated connections from other domains without trust relationships. Eg, RMAN running in the pre-production domain wouldn't be able to use a database account password to connect to an RMAN catalogue database in the production domain.
The Oracle database may be prevented from removing datafiles when a tablespace is dropped (including contents and datafiles) on Windows, even with Oracle 12.1.
12c can (and should) use managed service accounts for the Oracle Home User, but there isn't a lot of support information available. Here is my small contribution.
The performance consequences of sorting the result set from SQL using TO_CLOB are not easily found on the internet, so this is a brief note that might help make sense of AWR or ASH reports if the symptoms match.