Oracle Trouble Shooting Question and Answers

29. Describe the Oracle Wait Interface?
 
  • The Oracle Wait Interface is the set of data dictionary tables that store information about wait events.
  • Oracle offers multiple views to give information about wait events, such as v$system_event and v$session_event.
  • You can get the information about the wait events for the database or a specific session from these views and find out the event, which seems too high.
 
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30. Name a few places you will look to get more details on a performance issue?
  Oracle records the information about different kind of errors and the processes in the files, such as ALERT log, user process trace files and background process trace files.
 
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31. Which trace file is used for performance tuning and why?
 
  • User process trace file is used for performance tuning because it contains information about execution plan and resource consumption. This information can be used for performance tuning.
  • These files are located in the directory specified in the BACKGROUND_DUMP_DIRECTORY parameter.
 
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32. What are the different types of locking modes?
  Lock modes vary from 0 to 6 in order of increasing exclusively, given as follows:
  • No lock (0)
  • Shared Row Exclusive lock (3)
  • Shared lock (4)
  • Exclusive lock (6)
  • You can get the information on modes of TM and TX locks by using the LMODE and REQUEST columns. Both the locks use the same numbering for lock modes.
  • DML requires a Shared Row Exclusive lock, that is, TM-3.
  • DDL requires an Exclusive lock, that is, TM-6.
 
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