AIX: Query Becomes Progressively Slower over Time, Waits On Direct Path Read
Last updated on MAY 23, 2017
Applies to:Oracle Database - Enterprise Edition - Version 126.96.36.199.0 and later
IBM AIX on POWER Systems (64-bit)
- A query is taking twice as long to complete as it has in the past, and response time may appear to worsen, as time goes on.
- Examination of V$SESSION_WAIT indicates that the session is waiting on 'direct path read'.
- A "truss" of the server process which is handling the query indicates frequent occurrences of the function "aio_nwait_timeout64" with a return code greater than zero.
- Datafiles are mounted as a JFS2 file system with the CIO option. If not, they may be raw devices or may reside on ASM.
- A check of SMIT shows the following values for asynch I/O:
You may have recently upgraded the database from 10g, but not necessarily.
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