Oracle: Free buffer wait

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Data Block Cache lack free buffers

Tune by
Increase data blocks
Try to tune DBWR
If no ASYNC use I/O Slaves (dbwr_io_slaves)
Multiple DBWR (db_writer_processes)
Direct I/O
Improving Inefficient SQL
requesting large # of blocks

Finding a Free Block:

If the data block isn’t in cache
  • Get a free block and header in the buffer cache
  • Read it off disk
  • Update the free header
  • Read the block into the buffer cache

Need Free Block to Read in New Data Block

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