Oracle Managing Director Question and Answers

5. What is checkpoint?
 
  • A checkpoint is a point when a background process updates the headers of all datafiles and control files to synchronize the files.
  • At checkpoint, DataBase Writer (DBWR) writes the dirty buffers to the datafile.
 
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6. What is a locally managed tablespace?
 
  • A locally managed tablespace keeps track of its own block and maintains the information in a bitmap in the header section rather than in the data dictionary.
  • Each bit in the bitmap corresponds to a block or a group of blocks.
  • When the extends are allocated or freed for reuse, Oracle changes the bitmap values to show the new status of the blocks.
  • These changes do not generate rollback information because they do not update tables in the data dictionary, unlike the default method of Dictionary – Managed Tablespace.
 
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7. How would you force a log switch?
  A log switch can be forced by using the ALTER SYSTEM SWITCH LOGFILE; statement.
 
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8. What is row chaining?
 
  • Row chaining is a situation when a single row is stored in multiple blocks. It happens when row is too big to fit into a single block.
  • In other words, row chaining occurs when row size is greater than blocksize.
  • Tables with the LONG and LONG RAW columns are more likely to have chained rows.
  • In addition tables with more than 255 columns will have chained rows.
 
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