The JAVA_HEAP_SIZE option of the SET OPTION command sets the maximum size (in bytes) of that part of the memory that is allocated to Java applications on a per connection basis. Per connection memory allocations typically consist of the user's working set of allocated Java variables and Java application stack space. While a Java application is executing on a connection, the per connection allocations come out of the fixed cache of the database server, so it is important that a run-away Java application is prevented from using up too much memory.
The JAVA_NAMESPACE_SIZE option of the SET OPTION command sets the maximum size (in bytes) of that part of the memory that is allocated to Java applications on a per database basis. Per database memory allocations include Java class definitions. As class definitions are effectively read-only, they are shared among connections. Consequently, their allocations come right out of the fixed cache, and this option sets a limit on the size of these allocations.
