Skip to end of metadata
Go to start of metadata

Use

Avg read time <duration> ms for <number_of> reads on volume <volume_name>


Explanation

Generally in a tuned system data mainly should be read from the caches. Nevertheless, for some actions physical I/O is sometimes unavoidable. If it is necessary, the times for read I/O should not be higher than 10 ms for modern disks, usually smaller than 5 ms, if a lot of read operations are done.

Currently you will often find high priority warnings related to just a few read operations. If there is a high duration for just a few reads, it is usually not critical.


User Response

If you observe high read times related to a high amount of I/O you should check the disk architecture. Additionally a performance analysis could be helpful to check if unnessary physical I/O is caused by wrong optimizer strategies because of  disadvantageous access paths.


More Information

Relevant  DB-Analyzer FilesHelpful with ...
DBAN_IO.csv  Read and write operations to cache pages and data pages 
DBAN_IOTHREADS.csv Number and duration of physical write and read operations (I/O threads)
SAP Notes 
  
Expert SessionsContent / Helpful with ...
Session 26: SAP MaxDB I/O Concept  
Session 16: SAP MaxDB SQL Query Optimization (Part 1)
Session 16: SAP MaxDB SQL Query Optimization (Part 2 
Find detailed information about different optimizer strategies and performance optimization. 
Documentation (links) 
Optimizer
Search Strategies
 
  • No labels