features : esan3 zarch stfle msa ldisp eimm dfp edat etf3eh highgprs te 

An output line that lists edat  as a feature indicates 1 MB large page support. 

Defining huge pages with those kernel parameters allocates the memory as part of a pool. To monitor the pool usage, the information can be found using the cat /proc/meminfo  output. The two components that can benefit from the large frames are Java and Oracle. 

See the USE_LARGE_PAGES  initialization parameter in the Oracle documentation to activate huge pages in the database. 

The following kernel parameter in /etc/zipl.conf  enables 1 MB large frames: transparent_hugepage=never default_hugepagesz=1M hugepagesz=1M hugepages=<number of pages allocated at boot> 

Calculate the number of pages according to the application requirements. The number can be about three/fourths (3/4) of the memory to the instance. 

## 4.2.2 JAVA virtual machine tuning 

The IBM Java 1.8 package is the certified Java distribution for IBM LinuxONE with Temenos. Also, the IBM Java 1.8 JDK provides JIT compiler, which has shown in our lab environment to have a positive performance impact. 

## JVMs or Logical IFLs 

In our lab, it was noticed that a 1-1 allocation of JVMs to physical IFLs was a sweet spot when tuning the Transact application for maximum throughput. Considerations must be made based on the transaction mix for your environment. 

## Shared class cache 

Enable the use of a shared class cache between JVMs for AIT and JIT information. 

## Heap size 

Set the minimum (option -Xms ) and the maximum (option -Xmx ) JAVA heap size as the same. This ensures the heap size does not change during run time. Make the heap size large enough to accommodate the requirements of your applications but small enough not to impact performance. A heap size that is too large can also impact performance. You can run out of memory or increase the time that it takes the system to clean up unreferenced objects in the heap. This process is known as Garbage Collection. 

## IBM LinuxONE III Integrated Accelerator for zEDC 

This is a transparent exploitation of an integrated on-chip accelerator with no required setup. The prerequisite for using it is IBM Java 8 SR6. 

## Pause-less garbage collection 

Pause-less Garbage Collection (GC) is a new GC mode in the 64-bit IBM SDK for Java 8 SR5. Its purpose is to reduce the impact of GC stop-the-world  phases and improve the throughput and consistency of response times for Java applications. This technology leverages the new Guarded Storage Facility in IBM LinuxONE hardware to allow additional parallel execution of GC-related processing with application code. Pause-less Garbage Collection is particularly relevant for applications with strict response time Service Level Agreements (SLAs) or large Java heaps. 

