Today our developers were complaining about
performance issue , and there were nothing special which could cause high cpu
usage on server but there were many sessions with wait event "ASM
file metadata operation" and "ksv master wait'"...after googling
and digging the oracle support, finally found doc id (1308282.1)
related to problem with paramater "cell_offload_processing".. whydoes oracle use cell_offload_processing?
In Exadata Database Machine , Cell Offloading:The storage cells are saving the database node from processing some workload to inside them..this process can be referred to as cell offloading...In a Non-Exadata Oracle database , when someone selects a single column in a row , entire block related to row will be writting from the disks to buffer cache and then selected row will be extracted from this block..but Exadata database machine can pull desired rows from disks directly instead of writing entire block to buffer cache(this is also know as smart-scan)..Smart-scan can help to reduce I/O on database server.
But in a Non-Exadata Oracle
database, cell_offload_processing can be set as "FALSE" to solve this
problem...
"alter system set cell_offload_processing = false;"
This issue is also known as a bug and can be handled by applying Patch 11800170...
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Erol
