Oracle hot backup

When datafiles are put into hot backup mode, Oracle is still writing to them; this makes your average system administrator raise an eyebrow. Oracle slightly changes the way it performs updates to datafiles by copying whole datafile blocks, rather than just what has changed, into the online redo logs. Hot backups, by their very nature, take a corrupt copy of the datafiles. But relax, it’s OK. Since the instance is in ARCHIVELOG mode, all changes to the datafiles are available upon restore to correct any discrepancies created as the archiving process passes over any given datafile. This is why Oracle records redo information in whole blocks during hot backup: to help  recover any inconsistent blocks in the datafiles upon restore. 
User managed backup means you take backup without any oracle feature. Suppose if you take backup by Operating system then it is called user managed backup. And the term hot backup means taking your backup whenever your database is at open state.

To take full database backup follow the following steps.

1)Before proceed remember you can take online/hot backup whenever your database is in Archivelog mode. If your database run on noarchivelog mode then you must take consistent backup that is after cleanly shutdown. In order to determine the archival mode, issue the query..

SQL> SELECT LOG_MODE FROM V$DATABASE;
LOG_MODE
------------
ARCHIVELOG
If you see ARCHIVELOG then you can proceed further. In order to take backup while you are in noarhivelog mode follow other post on my blog.

2)Determine the files that you need to take backup.

Whenever you decide to take your database backup then take backup of data files , online redo log files ,control files, spfile.

In order to decide which files you need to backup issue the following query.

SQL>SELECT NAME "File Need Backup" FROM V$DATAFILE
UNION ALL
SELECT MEMBER FROM V$LOGFILE
UNION ALL
SELECT NAME FROM V$CONTROLFILE
UNION ALL
SELECT VALUE FROM V$PARAMETER WHERE NAME='spfile';

File Need Backup
--------------------------------------------------------------------------------
/oradata2/data1/dbase/system01.dbf
/oradata2/data1/dbase/undotbs01.dbf
/oradata2/data1/dbase/sysaux01.dbf
/oradata2/data1/dbase/users01.dbf
/oradata2/data.dbf
/oradata2/data1/data02.dbf
/oradata2/6.dbf
/oradata2/DBASE/datafile/o1_mf_l31sk0_.dbf
/oradata2/data_test.dbf
/oradata2/data1/dbase/redo03.log
/oradata2/data1/dbase/redo02.log
/oradata2/data1/dbase/redo01.log
/oracle/app/oracle/product/10.2.0/db_1/dbs/cntrldupbase.dbf
/oracle/app/oracle/product/10.2.0/db_1/dbs/spfiledupbase.ora
13 rows selected.

So after running the above query I can say I need to backup 13 files.

3)Take the tablespace in backup mode rather than offline and read-only tablespace. In case of offline and read only tablespace you do not have to place the tablespace in backup mode because the database is not permitting changes to the datafiles.

You can check the status, tablespace_name and it's associated data file name with the following query,

SELECT t.STATUS,t.TABLESPACE_NAME "Tablespace", f.FILE_NAME "Datafile"
FROM DBA_TABLESPACES t, DBA_DATA_FILES f
WHERE t.TABLESPACE_NAME = f.TABLESPACE_NAME;
ORDER BY t.NAME;

Take the tablespace in backup mode rather than offline and read-only tablespace.

You can easily make a script of taking the online tablespace in backup mode by following query.

SQL>SELECT 'ALTER TABLESPACE ' ||TABLESPACE_NAME ||' BEGIN BACKUP;' "Script" FROM DBA_TABLESPACES WHERE STATUS NOT IN ('READ ONLY','OFFLINE');

Script
-------------------------------------------------------------
ALTER TABLESPACE SYSTEM BEGIN BACKUP;
ALTER TABLESPACE UNDOTBS1 BEGIN BACKUP;
ALTER TABLESPACE SYSAUX BEGIN BACKUP;
ALTER TABLESPACE TEMP BEGIN BACKUP;
ALTER TABLESPACE USERS BEGIN BACKUP;
ALTER TABLESPACE TEMP_T BEGIN BACKUP;

6 rows selected.

Alternatively, you can issue

SQL>ALTER DATABASE BEGIN BACKUP;

4)Copy the datafile to backup location.

After making a tablespace in backup mode take backup/copy of the associated datafiles. Here you can also make a script in order to copy datafiles to another location.

For online tablespace you must at first take it backup mode. You can check whether backup mode now active or not by issuing following query,

SQL>SELECT t.name AS "TB_NAME", d.file# as "DF#", d.name AS "DF_NAME", b.status
FROM V$DATAFILE d, V$TABLESPACE t, V$BACKUP b
WHERE d.TS#=t.TS#
AND b.FILE#=d.FILE#
AND b.STATUS='ACTIVE';

SQL> SELECT 'host scp '|| FILE_NAME || ' &backup_location ' "Backup Command" FROM DBA_DATA_FILES;
Enter value for backup_location: /backup
old 1: SELECT 'host scp '|| FILE_NAME || ' &backup_location ' "Backup Command" FROM DBA_DATA_FILES
new 1: SELECT 'host scp '|| FILE_NAME || ' /backup ' "Backup Command" FROM DBA_DATA_FILES

Backup Command
------------------------------------------------------------------------------------------
host scp /oradata2/data1/dbase/system01.dbf /backup
host scp /oradata2/data1/dbase/undotbs01.dbf /backup
host scp /oradata2/data1/dbase/sysaux01.dbf /backup
host scp /oradata2/data1/dbase/users01.dbf /backup
host scp /oradata2/data.dbf /backup
host scp /oradata2/data1/data02.dbf /backup
host scp /oradata2/6.dbf /backup
host scp /oradata2/DBASE/datafile/o1_mf_l31sk0_.dbf /backup
host scp /oradata2/data_test.dbf /backup

9 rows selected.

Also you can backup network files. Do a recursive search for *.ora starting in your Oracle home directory and under it.

In order to make script for to copy data files for those tablespace which are only in backup mode then issue,

SQL>SELECT 'host scp '|| d.name ||' &backup_location' FROM V$DATAFILE d, V$TABLESPACE t, V$BACKUP b
WHERE d.TS#=t.TS#
AND b.FILE#=d.FILE#
AND b.STATUS='ACTIVE';

Run the script that you genereted.

On windows or other operating system you can use graphical browser to copy or other associated copy command.

5)Whenever you copy is finished make the tablespace out of backup mode. You can issue BEGIN BACKUP .. SCP serially (Take one tablespace in begin backup mode and then copy the associated datafiles and make the tablespace out of backup mode) or you can do it parallely(Take all tablespaces in begin backup mode and then copy the associated datafiles of all tabelspaces and then make the tablespace out of backup mode).

You here also make a script like,

SQL>SELECT 'ALTER TABLESPACE ' ||t.name ||' END BACKUP;' "End Backup Script"
FROM V$DATAFILE d, V$TABLESPACE t, V$BACKUP b
WHERE d.TS#=t.TS#
AND b.FILE#=d.FILE#
AND b.STATUS='ACTIVE';
End Backup Script
----------------------------------------------------------
ALTER TABLESPACE SYSTEM END BACKUP;

You if you have taken Database in backup mode then issue

SQL>ALTER DATABASE END BACKUP;