Oracle Trouble Shooting Question and Answers

13. What is the significance of latches with respect to performance tuning?
  • An Oracle process must acquire relevant latch in order to get resource allocated.
  • A latch is required for a very short amount of time to ensure that the resource is allocated.
  • Whenever there is a contention for latch, it indicates that there is a performance issue, which may be due to either of the two following reasons:
  • Lack of availability of resource.
  • Poor application programming resulting in high number of requests for resource.
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14. What is the use of ALERT log file?
  The ALERT log is a log file that records database wide events. The information in the ALERT log file is generally used for trouble shooting. Following events are recorded in the ALERT log file:
  • Database shutdown and startup information
  • All non default parameters
  • Oracle internal (ORA – 600) errors
  • Information about a modified control file
  • At log switch
  • The location of ALERT log file is specified in the BACKGROUND_DUMP_DEST parameter.
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15. How can you get more details about the blocking session?
  You can use the v$session or gv$session view in Real Application Clusters (RAC) environment to get the session information.
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16. What is a lock?
  • Lock is a mechanism provided by Oracle to reserve a database object so that different sessions do not interfere in each other's work.
  • Locking helps in ensuring data consistency and maintaining database objects in usable state in a multi user environment. However, it can cause one session to block another.
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