RMAN Q & A Page - 10

RMAN INTERVIEW QUESTIONS AND ANSWERS

                                                                     

                                                                    Page – 10

91. How do you configure RMAN backup for 100 GB database? How we would  estimate backup size backup time?

Check your actual size of your database for  RMAN backup size  almost depends on your actual size of database.

SELECT SUM(BYTES)/1024/1024/104 FROM DBA_SEGMENTS;

Backup time depends on you hardware configuration of your  server such as  CPU, Memory, and   Storage.

Later you can also minimize the backup time by configuring multiple channels with the backup scripts

92. Why use RMAN tool to backup and recover oracle Database?

Organization may have some wonderful  custom build unix script which may be backing up the  databases without any  issued, however from administrative  point  of view RMAN is supported by oracle and if have any issue with backup and recovery using RMAN you can always  rely on oracle debug.

RMAN can be used in two modes. RMAN can be operated as command-line  and Enterprise Manager based tool oracle  RMAN tool  has few interesting  features where you could  backup  only changed  blocks, that  avoid backing the entire database. This  method is called incremental  backups. When size  of the database is enormous incremental backup significantly  reduces the time taken to backup the database.

93 What are the difference  between crosscheck and validate commands?

Validate command is to examine the backup set and report whether it can be resorted. RMAN scans all of the  backup pieces  in the  specified backup sets and looks at the checksum to verify  that the contents are intact so that  backup can be successfully restored if necessary.

Crosscheck  command is to verify  the status of backups and copies recorded in the  RMAN repository against media  such  as  disk or tape.  The crosscheck command only process files created on the same device type as the channel running  crosscheck.

94. What is the difference  between  backup set and backup piece?

A). Backup set is logical  and backup piece is phycial

B). RMAN command  to backup for creating standby database

C). Duplicate target database

You can  loss one datafile and DB is running  in ARCHIVELOG mode. You have full database backup of  1 week / day  old  and don’t have  backup of this datafile(new).

95. How do you restore /  recover the backup?

Create  datafile and recover datafiles

SQL> alter  database create datafile ‘/u01/app/oracle/oradata/syz.dbf’ size 2 G;

RMAN > recover datafile file_id;

96   command  to delete archivelogs   older than 7 days?

RMAN> delete archivelog all  completed before sysdate-7;

97. How to view the current database ?

RAMN> Show  all;

98.  What Is the incremental checkpoint?

In incremental checkpoint  process, CKPT process records lowest low REA to the control file to  keep advancing  the buffer checkpoint  queue(BCQ) to make easy and faster active checkpoint queue(ACQ).

99. Does incremental  checkpoint recorded  in the alertlog? How to disable it?

Incremental  checkpoints in  alert_log we can enable  / disable  recording using parameter log_checkpoints_to_alert=true/false

100. What is the significance of  incarnation and DBID in the RMAN backup?

Incarnation help  to go backup to  old position of the database

DBID  means database id. Incarnation is effectively a new version of database  that happens  when you reset  the online redolog  using  alter….