Drop database Using RMAN command.

Run below command in RMAN prompt.  You must be connected to a target database and database is mount exclusive and not open. You need to start RESTRICT mode.

RMAN> connect target /

connected to target database: TEST (DBID=233344476, not open)

RMAN> SQL 'ALTER SYSTEM ENABLE RESTRICTED SESSION';

using target database control file instead of recovery catalog

sql statement: ALTER SYSTEM ENABLE RESTRICTED SESSION

RMAN> DROP DATABASE INCLUDING BACKUPS;

database name is "TEST" and DBID is 233344476

Do you really want to drop all backups and the database (enter YES or NO)? YES

allocated channel: ORA_DISK_1

channel ORA_DISK_1: SID=421 device type=DISK

specification does not match any backup in the repository

released channel: ORA_DISK_1

allocated channel: ORA_DISK_1

channel ORA_DISK_1: SID=421 device type=DISK

specification does not match any datafile copy in the repository

specification does not match any control file copy in the repository

specification does not match any control file copy in the repository

specification does not match any archived log in the repository

database name is "TEST" and DBID is 233344476

database dropped

Consuming most undo your database

Below Query find out SQL has run for the longest time in your database.

select  s.sql_text

 from  gv$sql s, gv$undostat u 

where u.maxqueryid=s.sql_id

Base on gv$transaction and gv$session find out most undo used in your database.

 

select   s.sid, s.username, t.used_urec, t.used_ublk 

 from   gv$session s, gv$transaction t

where  s.saddr = t.ses_addr  order by t.used_ublk desc;

Below query  which session is currently  using the most undo  in your database.

 

select  s.sid, t.name, s.value

 from  gv$sesstat s, gv$statname t 

where  s.statistic# = t.statistic#

    and  t.name = 'undo change vector size' order by s.value desc;

 

When you run above query base on output your find out which SID for the session  consuming the most undo.

 

If you want find out active transaction, you can user gv$transaction view.

 

select  sql.sql_text sql_text, t.USED_UREC Records,

           t.USED_UBLK Blocks, (t.USED_UBLK*8192/1024) KBytes

  from  gv$transaction t,  gv$session s,  gv$sql sql

where  t.addr = s.taddr 
    and s.sql_id = sql.sql_id 
    and s.username ='&USERNAME'

Base on above query output, number of undo records used(USED_REC) and undo blocks consumed  by a transaction (USED_UBLK).

 

Above query is based on RAC  Database. If you database is not in RAC, please user V$ views.