Noel

• May 29th, 2006

 

When we r taking  hot backup(begin backup - end backup) ,the datafile heder associated with the datafiles in the corresponding tablespace is frozen.So Oracle will stop updating the datafile header, but will continue to write data into datafiles.In backup oracle will generate more redos , this is beacause  oracle will write out complete changed blocks to the redo log files.

noyal

 Profile Answers by noyal 

• May 29th, 2006

 

The two things will happen when the tablespace in backup mode

1.) The datafile header associated with the tablespace in the backup up mode will be in frozen state.So it stops updating the datafile header, but it continually writes into the datafile.

2.) More redos are generated.This is because oracle will write all the changed blocks into the redo log.Normally only the changes are logged into the redo logs.

regards,

Noyal

Ritesh Raj Singh

• Jun 27th, 2006

 

Hi

Everyone ..Answer given by all others are right and i am just adding a brief to it. actually what happens in backend when a tablespace is put up in backup mode is that the all datafile belonging the tablespace gets their checkpoint frozen. which means that next time the recovery should start after the checkpoint anything after the checkpoint is roll backward or roll forward to maintain consistency. At the same time database writter process writes to the datafile all the data blocks and the same data blocks are written to redo log files this is because the oracle block size and OS block sizes differs which results in fractured block to be copied by the OS utilities and for that reason when the file backuped up by hot backup required recovery and any fractured blocks are found out they are replaced by the actual block from archived log which are copy of redo logs.RMAN doesn't requires the tablespace to be put in the backup mode because oracle understands the block size and skips the block if a process is making change to it at the time of the backup.when you put the tablespace end backup the checkpoint is released and marked wih current checkpoint No and in this way oracle maintains consistency in the database.

Regards

Ritesh Raj Singh

Database Administration Team

ICICI Ltd

ICICI Corporate House

Mahalakshmi Mumbai

09322070038

anamika6

 Profile 

• Aug 2nd, 2006

 

send me the details

Priyanka P

• Nov 1st, 2006

 

. while taking hotbackup (begin end backup) what will happend backend

2. You system performs a nightly backup of all the data in the /sales_data file system using ufsdump to an 8mm DAT tape. Recently, the backup stopped Answer: B

3. Which phrase best describes RMAN multiplexed backup sets? A. Stripes a single backup set across multiple channels. B. Identical copies of backup p Answer: C

4. Your supply chain software currently runs a standalone application which communicates to the backend services using IIOP. The new requirements Answer: C, D

5. how much time will it take a hotbackup if the batabase size is 60Gb

6. What is a logical backup?   Logical  backup  involves reading a set of database records and writing them into a file. Export utility is used for taking backup and I

7. What is Partial Backup ? A    Partial  Backup  is any operating system backup short of a full backup, taken while the database is open or shut down.

8. Your network has two Windows 2000-based WINS servers. How should you configure thenetwork to automatically backup the WINS database of both WINS serve

9. When you installed a patch, you had used /var/backup as the backup directory. Which command must you used to uninstall the patch ?a. patchrm /var/ba Answer: B

10. Examine this syntax which allocates channels during a parallel image copy: RMAN> CONFIGURE DEVICE TYPE disk parallelism 4: 2> COPY 3> d Answer: C

priyanka

• Sep 26th, 2007

 

When the database is taken in backup mode the checkpoint takes place and the datafile header gets frozen
As the checkpoint takes place the database writer writes all the blocks from database buffer cache to datafiles.The same blocks are also written from the redo log buffer in the redo log files. So the archive log generation becomes high
OS blocks differ from oracle blocks so there can be fractured block that needs recovery. This is the reason why all the blocks are written in the redolog files when the database is in backup mode