Oracle SQL Developer and missing ocijdbc11.dll

I had oracle express installed and also using SQL Developer. But when I tried to use any TNS name in its connection setup SQL Developer always complaints missing ocijdbc11.dll in java.library.path.

Searching internet and found the link:

So in short, just set %ORACLE_HOME% environment variable solved the problem.

Find Oracle DB Locking

First to find out the session that caused the locking. Use any of below two SQLs.

Once you have session id, query v$session to find SQL_ID or PREV_SQL_ID.

And get the query from v$sql

Check DB Logon History