RMAN Q & A Page – 4

RMAN INTERVIEW QUESTIONS AND ANSWERS

                                                                     

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31.What is logical backup?

Logical  backup is a process of extracting  data in the form of SQL statements, where it is useful  to recover in case the  objects are lost. The main drawback  of using  this  backup is that mean time to recover is high

32. suppose some blocks are damaged in a data file, can  you recover these blocks  if you are using RMAN?

Yes, the damaged blocks can be recovered

33. What is cancel based recovery?

Cancel based recovery is a user managed incomplete recovery where a user can apply the until cancel   clause to perform recovery until the user  manually cancels the recovery process. The process can be cancelled when  the user is sure that  no more recovery  is possible. Cancel based  recovery is performed  when  there is a requirement to recover the recovery process because the user can provide names of archive log files  to be used for recovery. Cancel based recovery can be performed  using the following statement

34. What is a complete recovery?

Complete recovery  uses redo data  or incremental backups combined with a backup of a database, data file, or tablespace to update it to the most current point in time.  Oracle applies all the redo changes contained  in the  archived  and online logs to the backup.

Druing a complete  recovery, all the changes made to the restored file since the time of  the  backup are re done

35. What are the common RMAN errors?

Some of the common RMAN errors are: 
RMAN-20242: Specification does not match any archivelog in the recovery catalog.
Add to RMAN script: sql 'alter system archive log current';
RMAN-06089: archived log xyz not found or out of sync with catalog
Execute from RMAN: change archivelog all validate;

36. How does one create a RMAN recovery catalog?

Start by creating a database schema (usually called rman). Assign an appropriate tablespace to it and grant it the recovery_catalog_owner role. Look at this example: 
sqlplus sys

SQL>create user rman identified by rman;

SQL> alter user rman default tablespace tools temporary tablespace temp;
SQL> alter user rman quota unlimited on tools;
SQL> grant connect, resource, recovery_catalog_owner to rman;
SQL> exit;
Next, log in to rman and create the catalog schema. Prior to Oracle 8i this was done by running the catrman.sql script. rman catalog rman/rman
RMAN>create catalog tablespace tools;
RMAN> exit;

You can now continue by registering your databases in the catalog. Look at this example: 
rman catalog rman/rman target backdba/backdba

RMAN> register database

37. What is cold backup? What are the elements of it?

Cold backup is taking backup of all physical files after normal shutdown of database. We need to take.
- All Data files.
- All Control files.
- All on-line redo log files.
- The init.ora file (Optional

38. What strategies are available for backing-up an Oracle database? 

The following methods are valid for backing-up an Oracle database: 
Export/Import - Exports are "logical" database backups in that they extract logical definitions and data from the database to a file.
Cold or Off-line Backups - Shut the database down and backup up ALL data, log, and control files. 
Hot or On-line Backups - If the databases are available and in ARCHIVELOG mode, set the tablespaces into backup mode and backup their files. Also remember to backup the control files and archived redo log files. 
RMAN Backups - While the database is off-line or on-line, use the "rman" utility to backup the database. 
It is advisable to use more than one of these methods to backup your database. For example, if you choose to do on-line database backups, also cover yourself by doing database exports. Also test ALL backup and recovery scenarios carefully. It is better to be save than sorry. 
Regardless of your strategy, also remember to backup all required software libraries, parameter files, password files, etc. If your database is in ARCGIVELOG mode, you also need to backup archived log files.

39. What strategies are available for backing-up an Oracle database?

The following methods are valid for backing-up an Oracle database: 
Export/Import - Exports are "logical" database backups in that they extract logical definitions and data from the database to a file.
Cold or Off-line Backups - Shut the database down and backup up ALL data, log, and control files. 
Hot or On-line Backups - If the databases are available and in ARCHIVELOG mode, set the tablespaces into backup mode and backup their files. Also remember to backup the control files and archived redo log files. 
RMAN Backups - While the database is off-line or on-line, use the "rman" utility to backup the database. 
It is advisable to use more than one of these methods to backup your database. For example, if you choose to do on-line database backups, also cover yourself by doing database exports. Also test ALL backup and recovery scenarios carefully. It is better to be save than sorry. 
Regardless of your strategy, also remember to backup all required software libraries, parameter files, password files, etc. If your database is in ARCGIVELOG mode, you also need to backup archived log files.

40. What is the difference between online and offline backups?  

A hot backup is a backup performed while the database is online and available for read/write. Except for Oracle exports, one can only do on-line backups when running in ARCHIVELOG mode. 
A cold backup is a backup performed while the database is off-line and unavailable to its users