Memory Parameters 

Use

The following parameters are used to set the memory management of the VM Container.

For a description of the various memory areas and their connection with the parameters see Memory Management in the VM Container.

●      Maximum size of the VM heap: vmcj/max_vm_heap_MB

●      Maximum size of the Java heap: vmcj/option/maxJavaHeap

●      VMC pool size: vmcj/option/ps

●      Size of the code cache of the JIT Compiler: vmcj/option/jit/sharedCodeCache

Features

The profile parameters are described below. You can change the values by changing the profile and restarting the VM Container (see VM Overview).

The standard settings represent a minimum configuration. You normally have to change these settings for productive operation of the VM Container. Configure the system following the settings in SAP Note1020539.

vmcj/max_vm_heap_MB

Each VM is mapped into a memory area that has a fixed size and is created during startup. The size determines how much memory a VM can allocate to its VM heap (local objects, Java stack, service stack, and so on). This parameter defines the size of this memory area.

Possible values: [size in MB]

Standard value: 64

If the maximum size is exceeded, the VM allocates local process memory (operating system heap). The memory cannot be assigned to another user, and remains occupied by the current user until the request is completed (PRIV mode, see Private Memory). Afterwards the VM closes.

Java stacks

You can change the size of the Java stack with parameter vmcj/option/ss = [size [k | M]]. The standard size is 128k on 32 bit platforms and 256k on 64 bit platforms.

Service stacks

The meaning of service stacks is described in vmcj/jni_strategy. The VM standard size is 1MB on 32 bit platforms and 2MB on 64 bit platforms.

vmcj/option/maxJavaHeap

Each VM is mapped into a memory area that has a fixed size and is created during startup. This parameter specifies how much memory a VM can allocate to its Java heap (local VM Java objects.) You can specify the size in KB or MB.

Possible values: [size [K | M]]

Default value: 64M

vmcj/option/ps

This parameter determines the size of the shared pool of the VM container. The pool is used by all VMs and contains shared classes, shared closures, and so on.

Possible values: [size [K | M]]

Standard value: 64M (32 bit) / 128M (64 bit)

vmcj/option/jit/sharedCodeCacheSize

Size of the shared memory in which the just-in-time compiler stores the machine code generated from the Java byte code. This memory area is used by all VMs and is located in the shared pool.

You can specify the size in KB or MB.

Possible values: [size [K | M]]

Default value: 32M