Usefull Oracle Commands

alter database mount;
alter database open;
alter database close;
alter database mount;
alter database dismount;
alter database open read only;
alter database mount exclusive;
alter database mount standby database;

Check oracle users status:
==========================
SELECT username,account_Status from dba_users;

Check Directory Path
====================
SELECT directory_path from dba_directories;
SELECT * from dba_directories;


Create Directory Path
=====================
create directory BACKUP_DIR as '/backup/dailybackup';
grant read, write on directory BACKUP_DIR to system;


Take Expdp Full Backup
======================
expdp system/manager full=y directory=BACKUP_DIR dumpfile='prodbk.dmp' logfile='prodbk.log';


EXPORT Backup of Tablespace
===========================
expdp hr/hr@ORCL     DIRECTORY=exp_tblsp  DUMPFILE=tablespace.dmp LOGFILE=tblsp_log.log TABLESPACES=USERS,EXAMPLE;
expdp system/manager DIRECTORY=BACKUP_DIR DUMPFILE=tablespace.dmp LOGFILE=tblsp_log.log TABLESPACES= PSIMAGE;


View Data Files
===============
col tablespace_name format a16;
col file_name format a36;
SELECT TABLESPACE_NAME, FILE_NAME, BYTES FROM DBA_DATA_FILES;


Check Tablespace online/offline status
======================================
SELECT TABLESPACE_NAME, STATUS, CONTENTS FROM USER_TABLESPACES;


Bring a Tablespace Offline/online
=================================
ALTER TABLESPACE my_space OFFLINE;
ALTER TABLESPACE my_space ONLINE;