Avg read time <duration> ms for <number_of> reads on volume <volume_name>
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.
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.
|Relevant DB-Analyzer Files||Helpful 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)|
|Expert Sessions||Content / 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.|