The memory size of the Explicit heap used in an application is estimated before you operate an application. Actually the memory size is estimated by checking an event log of the explicit management heap functionality after the application is operated. For details about how to estimate, see 7.11.3 Memory size used in the application.
When investigating the usage of the Explicit heap after the application is operated or is being developed, use the JavaVM log file and Java APIs. For details about the procedures for investigating after application development or operations, see 7.13 Errors that occur during the application of the Explicit Memory Management functionality and the solutions.