Basic HTML version of Foils prepared 7 October 97

Foil 29 Using Oracle 7 Server's PCM locks:

From Second Part of RDBMS Discussion ARL Database Tutorial -- February 98. by Gang Cheng Marek Podgorny Chao-Wei Ou
1 An instance acquires a PCM lock as a resource for update purposes
2 All buffer caches must contain the same copy of a resource
3 PCM blocks:
  • Ensure cache coherency by only allowing instances to change blocks while holding a lock
  • PCM lock work independently of transaction locks (row-level locking)
  • Ensure cache coherency using minimum amount of communication
  • PCM locks are allocated to files when a instance is started
  • Blocks are typical O/S disk blocks and of fixed size
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© on Mon Oct 13 1997