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Selects and fetches selectivity <percentage>%: <number_of> selects and fetches, <number_of> rows read, <number_of> rows qualified


The strategies for accessing table data are poor for SELECT or FETCH statements. The system has to read a large number of table rows to find a small number of rows that fulfill a WHERE condition.


User Response

Find the statement that causes this poor ratio of read rows to found rows, and check the access strategies for this statement.


More Information

Relevant  DB-Analyzer Files
Helpful with ...
DBAN_CACHES.csv Successful and unsuccessful accesses to caches, and also hit rates 
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)
DBAN_LOAD.csv Accesses and selectivity of SELECT, FETCH, INSERT, UPDATE, and DELETE statements 
SAP Note
Helpful with ...
Expert Sessions (Link to trainings)
Content / Helpful with ...
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.
Session 26: SAP MaxDB I/O Concept  
Documentation (links)
Helpful with ...
SQL Optimizer Search Strategies 



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