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User task <task_ID>: physical reads: <count> (<number_of> pages), <number_of> commands, <appl_pid_and_node>

User task <task_ID>: physical reads: <count> (<number_of> pages), avg read time <abs_duration> (<rel_duration>) ms, <number_of> commands, <appl_pid_and_node>

new as of 7.9.10 (PTS 1273758):

User task <task_ID>: physical reads by task: <count> (<number_of> pages), avg read time <abs_duration>  ms, <number_of> commands, <appl_pid_and_node>

User task <task_ID>: physical reads via dev threads: <count> (<number_of> pages), avg read time <abs_duration> (<rel_duration>) ms, <number_of> commands, <appl_pid_and_node>



Modified pages can be displaced from the data cache to the data area, because not all of the data used by the applications can be held in the data cache. If you observe a high number of physical reads you should check if the CacheMemorySize is defined high enough. Or if there is potential to optimize commands and find better access strategies to reduce the occupation of the cache.

Additionally the average read time is reported. If high values are shown check the hardware for I/O problems. You may ignore high read times if they only refer to a few read operations; then usually the shown avg value is not representative.


User Response

Increase the size of the cache.
Check I/O performance when you observe high read times. 


More Information

Relevant  DB-Analyzer Files
Helpful with ...
DBAN_IOTHREADS.csvFind more information about duration of physical read/write.
DBAN_IO.csv Statistics about the numbers of I/O operations.
SAP Note
Expert Sessions (Link to trainings)
Content / Helpful with ...
Session 27: SAP MaxDB Multi TaskingProvides general information about the concept of "cooperative" multi-tasking.
Session 26: SAP MaxDB I/O ConceptProvides general information about the MaxDB I/O concept.
Session 29: SAP MaxDB: Improvements in I/O Handling 7.9 and Prefetch Mechanism 
Documentation (Links)
Helpful with ...


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