Some quick tips on how to inspect what you have in your Oracle database.
-- show all schemas
select distinct owner from dba_segments where owner in
(select username from dba_users where default_tablespace not in ('SYSTEM','SYSAUX'));
-- show all tables from a schema/owner
select * from all_tables where owner = 'HR';
-- show table description
desc HR.EMPLOYEES;
-- show all users
select * from all_users;
select username, * from dba_users;
-- See who is taking up a DB lock
select c.*, b.* from v$lock a, dba_locks b, v$session c
where a.id1 = b.lock_id1 and b.session_id = c.sid
-- See internal SQL id
select * from v$sql
-- See Oracle latches:
select * from v$latch
-- See Library Cache of SGA (System Global Area) like buffer cache size:
select * from v$sgastat
-- See tx locks (TX) and DML locks (TM):
select * from v$lock where type in ('TX', 'TM')
select * from dba_locks where lock_type in ('Transaction', 'DML')
