DB2 UDB for z/OS Version 8 Performance Topics - IBM Redbooks

3.1.5 Conclusion
The performance improvement with multi-row insert is not as high as with multi-row fetch
since a row insert is more complex and costly than a row fetch.
The performance improvement using multi-row insert depends on:
► Number of rows inserted in one insert SQL statement
► Number of columns inserted (more improvement with fewer columns), data type and size
of columns.
► Number of indexes on the table
► For single-row insert, the measured CPU cost in V8 is the same as V7.
Multi-row fetch/update performance
Multi-row fetch/update measurements, where the whole rowset was updated, show a
behavior similar to multi-row fetch. The measurement values are in Table 3-1.
► Measurements, compared to V7, show
– 25% CPU time improvement with MR=10 rows
– 40% CPU time improvement with MR=100+ rows
The performance improvement is not as high as MR fetch since a row cursor update is more
complex and costly than a row fetch.
► Performance improvement depends on
– Number of rows fetched/updated in one SQL statement
– Number of columns fetched/updated
– Complexity of the fetch/update SQL statement
– Number of indexes updated
Multi-row fetch/delete performance
Multi-row fetch/delete measurements show a behavior similar to multi-row fetch. The
measurement values are in Table 3-1.
Measurements, compared to V7, show
► 25% CPU time improvement with MR=10 rows
► 35% CPU time improvement with MR=100+ rows
Performance improvement is not as high as MR fetch since a row cursor delete is more
complex and costly than a row fetch.
The performance improvement depends on:
► Number of rows fetched/deleted in one SQL statement
► Number of columns fetched
► Complexity of the fetch/delete SQL statement
► Number of indexes on the table
Multi-row operations allow DB2 V8 to reduce the traffic between the application program and
DB2 when compared to single-row operations. The measurements show better performance
improvement in the case of statements with:
► Less complex SQL and data types
► Fewer columns processed
Chapter 3. SQL performance 37