DB2 Express C 10.5.4 using up all memory for package cache
Many applications or persistence frameworks generate new statements for each interaction with the database. The DB2 statement concentrator can help save system resources by mapping similar statements to one and reusing access plans and thereby share resources. Usually this help to cut query compilation time and reduce required system resources.

The package cache size can either be automatically set (self-tuning memory manager) or manually specified. In your case it seemed manually setting made more sense as the cache was hoping to reuse statements. If it is set to a fixed value, cache entries would need to be removed for new statements. However, the rest of your system memory could have been assigned to a bigger bufferpool.