判断io等待是否需要优化

Identifying  IO Response Time
Oracle records the response time of IO operations as the "Elapsed Time" indicated in  specific wait events and statistics."Response time" and "elapsed time" are synonymous and interchangeable terms in this context.
Below is a list of some of the more popular wait events and their typical acceptable wait times (not an exhaustive list)
 
Wait Event R/W Synchronous
/Asynchronous
Singleblock/
Multiblock
Elapsed Time
(with 1000+ waits per hour)
control file parallel write Write Asynchronous Multi < 15ms
control file sequential read Read Synchronous Single < 20 ms
db file parallel read Read Asynchronous Multi < 20 ms
db file scattered read Read Synchronous Multi < 20 ms
db file sequential read Read Synchronous Single < 20 ms
direct path read Read Asynchronous Multi < 20 ms
direct path read temp Read Asynchronous Multi < 20 ms
direct path write Write Asynchronous Multi < 15 ms
direct path write temp Write Asynchronous Multi < 15 ms
log file parallel write Write Asynchronous Multi < 15 ms
         
Exadata Related        
         
cell smart table scan Read Asynchronous Multi < 1 ms
cell single block physical read Read Synchronous Single < 1 ms
cell multiblock physical read Read Synchronous Multi < 6 ms
         
         

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