7.11.3 Impact of using the Explicit Memory Management functionality when estimating memory size

The use of a function from the Application Server functions has impact on the memory size of the Explicit heap area. The following table describes how the estimations are affected when you use a specific function:

Table 7‒5: Impact on estimations according to the use of functions
No.	Function	Difference in the Explicit heap area according to the usage of function	Impact on estimation
1	Automatic release function of Explicit Memory Management (`-XX:+HitachiExplicitMemoryAutoReclaim` option)	When enabled JavaVM uses the "`size-of-the-Survivor-area-of-java-heap` ×`2`" areas in the Explicit heap area. When disabled JavaVM does not use the Explicit heap area.	The estimated size of the final Explicit heap area when the function is enabled, is a value where "`size-of-the-Survivor-area-of-Java-heap`×`2`" is added to the estimated size calculated from the statistical information.
2	Automatic allocation functionality of the Explicit Memory Management functionality (`-XX:+HitachiAutoExplicitMemory` option)	When enabled The minimum size of Explicit memory block is 16 kilobytes. When disabled The minimum size of Explicit memory block is 64 kilobytes. Furthermore, how to allocate the Explicit heap area differs depending on the enabling and disabling of function. However, enabling and disabling does not have an impact on the estimations. When enabled The memory size specified in the `-XX:HitachiExplicitHeapMaxSize` option is allocated when starting the process. When disabled Only the required memory size is allocated when acquiring the Explicit memory block.	The information related to Explicit heap size that is output to statistical information differs depending on the enabling and disabling of function.

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