SAP DATABASE INTERVIEW QUESTIONS & ANSWERS -2

SAP DATABASE INTERVIEW QUESTIONS & ANSWERS -2



 
(Q) Can RMAN recover the Database automatically without Recovery catalog ?
(A) NO

(Q) Is whole Backup can be consider as level 0 Backup ?
(A) Whole backup is not level 0 Backup and can’t be used as basis for Incremental Backup.

(Q) Why do we need to perform a preparatory run ?
(A)  If Backup with RMAN is supposed to form sets then we need to run Preparatory run.
     Preparatory run can be run from DB13 prepare for RMAN Backup.
     No Backup is created during preparation run, only estimates Compression rate of BRTOOLS to compress the files and to determine compressed and decompressed file sizes.
     It is recommended to perform preparatory run per one Backup cycle.

(Q) What are the contents of tape lable after a tape is Initialized ?
(A) (i) Tape Name
    (ii) Name of the Database
    (iii) Time stamp of last backup recorded on the tape
    (iv) Number of Backups performed with the tape

(Q) Before writing data to tape if the lable is Red to check the following
(A)(i)    Tape Name
   (ii)    Tape Locked or Expired(Expire_period)
   (iii) No. of times the tape already been read(Tape_use_count)
    If Expiration_period = 0 days, the Volume is not locked at all and can be over written
    • If a lock occurs on a tape, it automatically expires at midnight.

(Q) What are the methods used by BRBACKUP and BRARCHIVE to check tape locks ?
(A) There are 2 types of locks
       (i) Physical lock check: Physical lock check is done by checking tape label parameter Expir_period. If the number of days passed since the tape was last used is less than value of parameter Expir_period, then the tape is physically locked.
       (ii) Logical lock check: This value is derived from the time stamp written to tables SDBAH, SDBAD

(Q) What are the various tape selection processes ?
(A)   (i) Auto tape selection BRBACKUP and BRARCH
      (ii) Manual selection by the Operator
      (iii)By external tool

(Q) What is the option to select the tapes automatically by BRBACKUP and BRARCH ?
(A) Set the parameter Volume_Backup and Volume_archive to TAPE

(Q) What is the command to check which tape will be automatically selected ?
(A) BR Backup |  BRARCHIVE –Q | Query { check }

(Q) How do we switch off automatic tape Management ?
(A) By setting up the parameter(Volume Backup and Volume Archive) to the value “SCRATCH”

(Q) How do I turnoff the tape management performed by SAP tools ?
(A) Configure the parameter Backup_dev_type= UTIL_FILE
                                    OR
    UTIL_FILE_ONLINE and also configure BACKINT interface in init<SID>.sap
NOTE: BackINT Interface program is only supported for external Backup.

(Q) How do we verify Backups ?
(A) Verification of backups is of 2 types
     (i) Tape Verification: The files are restored file by file and compared with original files to verify if the backup is redable.
     (ii) DB Block consistency: This checks the Database block by block using Oracle tool “DBVERIFY” to identify and restore from bad blocks.
     PATH: BRTOOLSBackup & DBcopyVerification of DB Backup, Verification of Archive log Backup
     The option USE_DBV(DBVERIFY=NO), only tape is verified (If yes Tape verification + DB Block Consistancy Check)

(Q) If SAP started and I am trying to switch to non-archive mode what will happen.
(A) It will show an error showing that SAP instance is running. Please showdown first or use force option.

(Q) If SAP is running and I try to shutdown the DB using BR tools what will happen.
(A) It through an error saying that SAP is running please shutdown the SAP first or force option and then continue.

(Q) If table space is full then what are the possibility to extend the table spaces ?
(A) Option 1: Add another data file to table space
           2: Existing data file can be manually resized
           3: Properties of existing data file can be changed to auto extendable

(Q) What id the formula to increase the data files size ?
(A) Data file size = Expected DB/100

(Q) How many number of data files will be there by default ?
(A) Default there are 100 data files

(Q) What is the error related with table flow ?
(A) For table ORA1653, ORA1654 for indexes.

(Q) Create server parameter file from init<sid>.ora
(A) Login to oracle user (ora<sid>)

SAP DATABASE INTERVIEW QUESTIONS & ANSWERS -1

SAP DATABASE INTERVIEW QUESTIONS & ANSWERS -1


(Q) what is the size of oracle data block ?
(A) 8 KB (fixed size)

(Q) What are the situations in which DBWO writes dirty blocks to disks ?
(A) If the number of scanned buffers reaches a certain thresh hold.
    At a specific time that is when check point occurs.

(Q) What are the conditions in which log writer writes redo log buffer data to online redo log files ?
(A) There 4 conditions:
    When transaction is committed.
    For every three seconds.
    When redo log is 1/3rd of full.
    When DBWR is about to write modified buffers to disk and some of the corresponding redo records have not at been written to online redo log i.e. write ahead logging.

(Q)What are the entries in co files ?
(A) Physical structure of database
      State of  database
      Table space information
      Names and location of data files and redo log files.
      Current log sequence number

(Q) Why do I need ‘SPFILE<SID>.ora’ even though I have ‘init<SID>.ora ?
(A) From Oracle 9.i ‘init<SID>.ora’ is replaced by ‘SPfile<SID>.ora or ‘SPfile.ora.

(Q) If a file is missing from the chain of offline Redo log files, then what we’ll do ?
(A) We have to perform a restore and recovery of Database. Recovery is performed using the method   “Point In Time” by which all the Offline Redo log files older than the last one is used for recovery.

(Q) What are the causes for logical errors related to Database ?
(A) (i) Manually deleting parts of Database objects such as Rows in a table.
      (ii) Manually dropping Database Objects.
      (iii) Manually dropping Application Objects.

(Q) Is Point in Time Recovery a standard Solution for logical errors in production system ?
(A) NO

(Q) Where do we use the Point IN Time Recovery ?
(A) Point in Time is very critical in a system landscape with Data Dependencies between Systems.

(Q) How do we verify Consistency of Oracle Database ?
(A) By performing by a logical data check.

(Q) Why do we need to perform a logical check ?
(A) In order to verify corrupted Data blocks (Ora – 1578)

(Q) Why do we need to perform a physical Data check ?
(A) To verify the tapes used for Database backup.

(Q) How often we perform Online Backup and Offline Backups ?
(A) Online Backup = Daily
      Offline Backup = Once in a Week

(Q) How do we perform Backup of Offline Redo log files ?
(A) (i) Backup of every Offline Redo log files is taken TWICE on separate tapes before the files are deleted from Archive Directory.
    (ii) Perform additional Backups after each system upgrade and also if Database structure is Modified.

(Q) What are the tools used by Oracle Admin in an SAP System for Backups ?
(A) Database Backups = BRBACKUP
      Offline Redo log files = BRARCHIVE

(Q) What are the occasions in which changes to Tile Structure of Database is made ?
(A)  1) When a Data file is added
       2) When a Data file is moved to a Different Location.
       3) When a Table Space and its Data files are reorganized.

(Q) What are the various Backup types ?
(A) There are 5 Backup types
     1) Online Backup
     2) Offline Backup
     3) Complete Backup
     4) Incremental Backup
     5) Partial Backup

(Q) If the Corresponding Full Backup is already overwritten and can I use Incremental Backup ?
(A) NO, Incremental Backup is useless.

(Q) Can I perform a Backup of Individual data files using Incremental Backups ?
(A) NO

(Q) What are the various Backup strategies used in SAP ?
(A) There are 3 Backup strategies in SAP
     i) Complete Backup:- Restore missing Database files from complete Backup, Restore Offline Redo Log files writte during and after this Backup.
     ii) Incremental Backup:- Restore missing Data files from last Full Backup, update them with restore from last Incremental Backup.
     iii)Partial Backup:- Replace complete backup with partial Backups , we need a longer time to perform a recovery from media crash.