I've now had this issue a couple of times. I execute a rather simple query and PL/sql developer seems to execute this and the execution timer walks, but on the database nothing seems to happen. There is a session on the database, which is not active. When I kill this session or press abort query the timer just keeps walking.

The only way to stop this is by force close PL/SQL Developer.

To obtain some more diagnostic information, can you modify the PL/SQL Developer shortcut and add the DebugSQL parameter? For example:

"C:\Program Files\PLSQL Developer 15 Beta\plsqldev.exe" DebugSQL

Reproduce the problem and send me the debug.txt file that is generated in the %APPDATA%\PLSQL Developer 15 directory (e.g. C:\Users\<User>\AppData\Roaming\PLSQL Developer 15).

I have sent the requested debug information.