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GeekInterview.com > Interview Questions > Database > Database Admin
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Question: Fractured Block
Answer: What is mean by fractured block in terms of manual hot backup? |
| March 03, 2008 00:26:13 |
#1 |
| gboyapalli |
Member Since: March 2008 Total Comments: 1 |
RE: Fractured Block
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A block fracture occurs when a block is being read by the backup and bieng written to at the same time by the DBWR. This happens because OS reads blcoks at a different rate than Oracle. your OS copy will pull pieces of an Oracle block at a time. What if the OS copy pulls half a block, and while that is happening, the block is changed by DBWR? When the OS copy pulls the second half of the block it will result in mismatched halves, which Oracle would not know how to reconcile. This is also why the SCN of the datafile header does not change when a tablespace enters hot backup mode. When receovery occurs the fractured data file block will be replaced with a complete block from redo.
I hope this helps;
-GB |
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