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You can recover a dropped schema if flashback is enabled for your database.The main advantage here is that you won't lose any data,but you have to go for a downtime until you finish the entire operation.
Make sure that the database is in flashback mode

SQL> select name from v$database;

NAME

---------

DIREC

SQL> select flashback_on from v$database;

FLASHBACK_ON

------------------

YES

SQL> alter session set nls_date_format='DD-MON-YYYY HH24:MI:SS';

Session altered.

SQL> select oldest_flashback_scn,oldest_flashback_time from v$flashback_database_log ;

OLDEST_FLASHBACK_SCN OLDEST_FLASHBACK_TIM

-------------------- --------------------

133450557 27-JUN-2016 16:29:59

To simulate the issue lets create few tables in a existing user and then drop it.

SQL> conn mahi

Enter password:

Connected.

SQL> create table flashback_testing ( col1 varchar2(20));

Table created.

SQL> insert into flashback_testing values ( 'flashback testing');

1 row created.

SQL> commit;

Commit complete.

SQL>

SQL> alter session set nls_date_format='DD-MON-YYYY HH24:MI:SS';

Session altered.

SQL> select sysdate from dual;

SYSDATE

--------------------

27-JUN-2016 19:49:12

SQL> conn / as sysdba

Connected.

SQL> drop user mahi cascade ;

User dropped.

SQL>

Let’s create some new user at this point- this is to ensure that our data are still intact at the end of this practice.

SQL> create user mahi_second identified by mahi;

User created.

SQL> grant dba to mahi_second ;

Grant succeeded.

SQL> conn mahi_second/mahi

Connected.

SQL>

SQL> create table t1 (id number );

Table created.

SQL> insert into t1 values (222);

1 row created.

SQL> commit ;

Commit complete.

SQL> select * from t1;

----------

222

In order to recover lost schema, use the flashback database feature to a time approximately before the user dropped.

SQL> conn / as sysdba

Connected.

SQL>

SQL> shut immediate ;

Database closed.

Database dismounted.

ORACLE instance shut down.

SQL>

SQL> startup mount;

ORACLE instance started.

Total System Global Area 4294967296 bytes

Fixed Size 5291928 bytes

Variable Size 2717909096 bytes

Database Buffers 1560281088 bytes

Redo Buffers 11485184 bytes

Database mounted.

SQL> flashback database to timestamp to_date('27-JUN-2016 19:50:00','DD-MON-YYYY HH24:MI:SS');

Flashback complete.

Following output from the alert log

Open the database in Read Only mode

SQL> alter database open read only;

Database altered.

SQL> conn mahi_second/mahi

ERROR:

ORA-01017: invalid username/password; logon denied

Warning: You are no longer connected to ORACLE.

Could see that we lost new user(mahi_second) that we created after droping the mahi user .

Check for the mahi user and its corresponing data

SQL> conn mahi

Enter password:

Connected.

SQL> select * from flashback_testing;

COL1

--------------------

flashback testing

SQL> conn / as sysdba

Connected.

Take an export of the user using traditional exp utility –note that expdp wont work when database in read only mode.

[oracle@exbdb01]:[DIREC1] $ exp owner=mahi file=/t3_nfs/REC/mahi_schema_bkp.dmp

Export: Release 12.1.0.2.0 - Production on Mon Jun 27 20:03:28 2016

Username: / as sysdba

Connected to: Oracle Database 12c Enterprise Edition Release 12.1.0.2.0 - 64bit Production

With the Partitioning, Real Application Clusters, Automatic Storage Management, OLAP,

Advanced Analytics and Real Applicat

Export done in US7ASCII character set and AL16UTF16 NCHAR character set

server uses AL32UTF8 character set (possible charset conversion)

About to export specified users ...

. exporting pre-schema procedural objects and actions

. exporting foreign function library names for user MAHI

. exporting PUBLIC type synonyms

. exporting private type synonyms

. exporting object type definitions for user MAHI

About to export MAHI's objects ...

. exporting database links

. exporting sequence numbers

. exporting cluster definitions

. about to export MAHI's tables via Conventional Path ...

. . exporting table FLASHBACK_TESTING 1 rows exported

. . exporting table QRC_TAB 5 rows exported