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Hello sir,
I installed the oracle 9i database and taken a backup using user managed way,I had taken the backup when database was running.
Now,I need to recover the database but the data which I lost due to failure is not being recovered. I think,there is some destroyed files has been copied.
I need to recover those data again,how would I do that.
Please suggest me some tools and trick regarding this.
The database backup and recover process is more and more sensitive thing for database administrator.You can take the back up of database in two ways-
User managed and RMAN backup and the user managed can be taken in closed and open both.
During the user managed backup ,one of the view is provided by the oracle database which can help you track the current backup position.
The view contains different columns which interacts with the current position of the backup.The view called as "V$BACKUP".
The query will show all the possible columns which you can use to know the condition of backup and name of file or tablespace which isCode:SQL> Desc V$BACKUP ;
continue or has been done.
User manged backup
The use manged backup can take much time if you have a heavy database and performing more and more operations.In the user managed backup,the redo logs are continuously generating because database is running and users are making query on the running database.
In this situation,the database follow a strategy of backup in the open mode using some conceptual statements -
SQL> ALTER DATABASE BEGIN BACKUP <Name_of_Tablespace>;
SQL> ALTER DATABASE END BACKUP <Name_of_Tablespace>;
These two statements are used to take the backup which is taking parallel way.otherwise more and more redo can decrease the performance and other functionality of database.
DBVERIFY Utility in backup processing
DBVERIFY,an external command-line utility which investigate the integrity checking of data structure.It is also used to check the validity of files which has been backed up.it checks that the particular file is able to use in recovery phase or not.
The command-line of DBVERIFY uses two interfaces -
1- The first interface,used to verify disk blocks for a single data file.
2- The second interface,used to allocate a segment for checking.
Using DBVERIFY command line interface:
I am going to show you a simple example to use DBVERIFY command line interface for a data file.The file would be scanned and after all the result will tell you the output at the block level.As a Long discussion,This is very clear,DBVERIFY utility is closely related and dependent on the operating
system.
The command which would be used to verification of a data file would be as follows:
The FEEDBACK shows "display single period (.) for every 100 pages completed.The pages specified the operatingCode:SQL> % dbv FILE=t_db1.dbf FEEDBACK=100
system component.
Output of the command :
During the execution of this command,the following output would be shown on your screen for your file verification-
Where the meaning of particular parameters in output would be as follows:Code:DBVERIFY - Verification starting : FILE = t_db1.dbf
................................................................................
DBVERIFY - Verification complete
Total Pages Examined : 8255
Total Pages Processed (Data) : 2045
Total Pages Failing (Data) : 0
Total Pages Processed (Index): 733
Total Pages Failing (Index): 0
Total Pages Empty : 5686
Total Pages Marked Corrupt : 0
Total Pages Influx : 0
Pages = Number of Blocks
Examined = Number of blocks in the data file
Processed = Verified blocks
Failing = The blocks which has been failed during checking
Marked Corrupt = The blocks for which the cache header is invalid
Influx = The blocks which is read and written at the point of time.