Typically, the map development system creates an instance of a map to process each transformation of data between the source and destination business objects. When the instance completes the handling of the transformation, the system frees up its resources. To reduce memory usage, the IBM system recycles an instance of a map instance by caching it and reusing it when the same type of map is instantiated at some later time. When the IBM system can recycle an existing map instance, it can avoid the overhead of map instantiation, thereby improving overall system performance and memory use.
Restrictions: The map development system automatically caches a map instance; that is, a map instance uses the Map Instance Reuse option by default. However, the Map Instance Reuse option imposes the following programming requirements on the map:
A global variable is a variable you declare in the Map local declaration block area of the General tab in the Map Properties dialog.
If you cannot define your map so that it meets the preceding restrictions, you must disable the Map Instance Reuse option for this map. To disable this option, remove the check mark from the Map instance reuse box, which appears in the map's Map Properties window in System Manager. This window also allows you to specify the size of the map-instance pool.