If the lookup table is on the same database as the source table in your mapping and caching is not feasible, join the tables in the source database rather than using a Lookup transformation.
If you use a Lookup transformation, perform the following tasks to increase performance:
· Use the optimal database driver.
· Cache lookup tables.
· Optimize the lookup condition. (<,>,<=,>=,!=)
· Filter lookup rows.
· Index the lookup table.
· Optimize multiple lookups.
Using Optimal Database Drivers
The Integration Service can connect to a lookup table using a native database driver or an ODBC driver. Native database drivers provide better session performance than ODBC drivers.
Caching Lookup Tables
If a mapping contains Lookup transformations, you might want to enable lookup caching. When you enable caching, the Integration Service caches the lookup table and queries the lookup cache during the session. When this option is not enabled, the Integration Service queries the lookup table on a row-by-row basis.
The result of the Lookup query and processing is the same, whether or not you cache the lookup table. However, using a lookup cache can increase session performance for smaller lookup tables. In general, you want to cache lookup tables that need less than 300 MB.
Complete the following tasks to further enhance performance for Lookup transformations:
· Use the appropriate cache type.
· Enable concurrent caches.
· Optimize Lookup condition matching.
· Reduce the number of cached rows.
· Override the ORDER BY statement.
· Use a machine with more memory.
Optimizing the Lookup Condition
If you include more than one lookup condition, place the conditions in the following order to optimize lookup performance:
Filtering Lookup Rows
Create a filter condition to reduce the number of lookup rows retrieved from the source when the lookup cache is built.
Indexing the Lookup Table
The Integration Service needs to query, sort, and compare values in the lookup condition columns. The index needs to include every column used in a lookup condition.
You can improve performance for the following types of lookups:
Cached lookups. To improve performance, index the columns in the lookup ORDER BY statement. The session log contains the ORDER BY statement.
Uncached lookups. To improve performance, index the columns in the lookup condition. The Integration Service issues a SELECT statement for each row that passes into the Lookup transformation.
Optimizing Multiple Lookups
If a mapping contains multiple lookups, even with caching enabled and enough heap memory, the lookups can slow performance. Tune the Lookup transformations that query the largest amounts of data to improve overall performance.
To determine which Lookup transformations process the most data, examine the Lookup_rowsinlookupcache counters for each Lookup transformation. The Lookup transformations that have a large number in this counter might benefit from tuning their lookup expressions. If those expressions can be optimized, session performance improves.