Oracle Database Administrator Job Interview Questions #2

1. Can you distinguish Redo vs. Rollback vs. Undo?

There is always some misunderstandings when referring to Redo, Rollback and Undo. They  all  sound like basically  the same thing  or at least fairly  close.

Redo: Every Oracle information source has  a  set  of (two  or more)  redo log data files. The redo log records all   changes   created   to   information,    such   as   both uncommitted    and  dedicated   changes.   In  addition   to the  online   redo  records  Oracle  also  shops  database redo  records.  All  redo  records  are  used  in  restoration situations.

Rollback:  More specifically   rollback  sections.  Rollback sections   shop  the   information    as  it  was  before  the changes  were created.  This is on the  other  hand to the redo log which  is a record of the  insert/update/deletes.

Undo: Rollback  sections.  They  both  are  really  one  in the  same.  Undo is saved  in the  undo tablespace.   It is helpful  in building  a read reliable  view of information.

2. What is Secure Exterior Password Store (SEPS)?

Through  the use of SEPS you   can   shop   security password    qualifications     for    linking    to    information source by  using  a customer   side  oracle  pockets,  this pockets   shops    deciding    upon    qualifications.     This feature  presented  since oracle  109. Thus the  applying concept,   planned   job,   programs    no   more   needed included   login   name   and   security    passwords.   This decreases  risk  because  the  security   passwords  won't be revealed    and   security    password    management coverage    is  more   easily   required   without    changing program concept  whenever  details  change.

3. What are the variations between Physical/Logical stand by databases?  How would you decide which  one is most suitable  for your environment?

Physical stand  by DB:

  • As the  name,  it  is actually   (datafiles,   schema,  other actual identity)      same     duplicate      of    the     main information source.

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  • It is synchronized with the main information source with Implement Redo to the stand by DB.
Logical Standby  DB:
  • As the  name  sensible  information   is the  same as the development    information   source,  it  may  be  physique can be different.

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  • It synchronized with main information source though SQL Implement, Redo caused by the  main information source into SQL claims and then performing these SQL claims on the stand by DB.

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  • We can  start  "physical   stand  by  DB to  "read  only" and  create   it  available   to  the   programs   customers (Only  choose  is permitted   during  this  period).  we can not apply   redo  records  caused  by  main   information source at now.

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  • We do  not  see  such  issues  with  sensible  stand  by information  source.   We   can   start    the   information source  in normal  method  and create  it available  to the customers. At  the   same   time,   we  may   use  stored records  caused  by main  information   source.-  For OLTP huge deal  information    source  it  is  better   to  choose sensible stand  by information   source.
4. Aware. log displaying this mistake "ORA-l109 signalled during: modify information source close". What is the key  good purpose why behind it?

The ORA-I 109 mistake just indicates that the information source is not start for company. You'll have to start  it up before you can continue.
 
It may  be while  you  are closing  down  the  information source,   somebody    trying    to   start    the   information source  respectively.   It  is  failing   attempt   to  start   the information   source  while  shut  down  is on the  way.Wait for the  a chance  to actually  shut  down the  information source  and  start  it  again  for  use.  On the  other  hand you  have  to  reboot  your  oracle  services  on  windows atmosphere.

5. Which factors are to be considered for creating catalog on  Table? How to  choose line for  index?

Creation  of catalog  on desk  relies  upon  on dimension desk, number  of information.   If dimension  desk is huge and  we  need  only  few  information   for  choosing  or  in review  then   we  need  to  develop   catalog.   There  are some  basic  purpose   of  choosing   line  for  listing   like cardinality   and regular  utilization   in where  condition  of choose  question.   Business  concept   is also  pushing  to develop   catalog   like  main   key,  because  establishing main  key  or  exclusive   key  instantly   create  exclusive catalog.

It is worth  noting  that  development   of so many  indices would    change   the    performance     of   DML   on   desk because   in  single   deal  should   need  to   perform   on various  catalog  sections  and desk simultaneously.

6. How  can  you  management     variety   of  datafiles in oracle  database?

The  db_files  parameter   is a "soft  restrict"     parameter that  manages  the  most of actual  OS data files that  can map   to    an    Oracle    example.     The    maxdatafiles parameter  is  a  different    -   "hard   limit"    parameter. When  providing  a "create  database"  control,  the value specified for    max   data   files    is   saved    in   Oracle management data  files  and standard  value  is 32. The most of  information   source  data  files  can  be set  with the init  parameter  db_files.

Regardless  of  the  setting   of  this  parameter,    highest possible  per  database:   65533  (May  be  less on  some working  systems),  Maximum variety  of datafiles  per tablespace:   OS reliant  = usually  1022

You can also by Limited  dimension   information   source prevents  and  by the  DB_FILES initialization   parameter for a  particular    example.   Big  file   table   spaces  can contain only  one data  file,  but  that  data  file  can have up to 4G prevents.

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