2.11.1 Overview of JavaVM functionality

The processes of a batch server that operates with Application Server are executed on JavaVM.

JavaVM is an independent JavaVM provided by Cosminexus Developer's Kit for Java that is the component software. The following table describes JavaVM functionality. For details on the functionality, see Reference location.

Table 2‒31: JavaVM functionality
Functionality	Explanation	Reference manual^#	Reference location
Explicit Memory Management functionality	You can place Java objects for which Full GC can occur in the Explicit heap area. This can prevent Full GC from occurring due to Java objects used in the application.	This manual	Chapter 7
Class-wise statistics functionality	You can output size of all instances in the members, possessed by instance of each class, to extended thread dump as class-wise statistics. By outputting class-wise statistics multiple times, you can check, for example, how Java objects change when GC occurs and the states of short-life Java objects. The functions that output class-wise statistics include the following: instance statistical functionality, static member statistical functionality, reference-related information output functionality, function for selecting GC prior to statistics output, unused objects statistical functionality in the Tenured area, base object list output functionality for Tenured augmentation factors.	Maintenance and Migration Guide	9.3
Class-wise statistics analysis functionality	Based on class-wise statistics output to extended thread dump, you can output total size of instances for each class and number of instances for each class as two types CSV files.		9.10
Functionality for output age distribution information of Survivor area	The age distribution information for the Java objects in the Survivor area can be output to a Java VM log file when copy GC occurs. You can check usage status of Survivor area and use for tuning the memory size.		9.11
hndlwrap functionality	You can inhibit occurrence of logoff events of JavaVM during logoff.		9.12

# uCosminexus Application Server is omitted in the manual name mentioned in Reference manual.

In JavaVM, log output contents are extended so that you can use the contents for analyzing the causes of failures and checking system status. This log is output to JavaVM log file. You can acquire a lot of troubleshooting information also from standard JavaVM. The availability of a system can be improved by using this log (extended verbosegc information) and performing appropriate tuning. For details on JavaVM log file, see 4.10 JavaVM log (JavaVM log file) in the uCosminexus Application Server Maintenance and Migration Guide. For details on the JavaVM tuning, see 7. JavaVM Memory Tuning in the uCosminexus Application Server System Design Guide.

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