Heap Memory Manager

A heap memory manager is responsible for the management of heap memory.

The heap memory manager performs the following fundamental memory operations:

Allocation - performed by malloc and calloc
Deallocation - performed by free
Reallocation - performed by realloc

The ILE runtime provides three different heap memory managers:

Default memory manager - a general-purpose memory manager
Quick Pool memory manager - a pool memory manager
Debug memory manager - a memory manager for debugging application heap problems

In addition, each of the memory managers has two different versions - a single-level store version and a teraspace version. In most cases, the two versions behave similarly except that the single-level store version returns pointers into single-level store storage and the teraspace version returns pointers into teraspace storage. The single-level store versions are limited to slightly less than 16 MB for a single allocation. The single-level store versions are also limited to slightly less than 4 GB for the maximum amount of allocated heap storage. The teraspace versions are not subject to these limitations. For additional information about single-level store and teraspace storage, please refer to the ILE Concepts manual.

The default memory manager is the preferred choice for most applications and is the memory manager enabled by default. The other memory managers have unique characteristics that can be beneficial in specific circumstances. Environment variables can be used to indicate which heap manager to use as well as to provide heap manager options. In some cases, functions are also available to indicate which heap manager to use.

Note: The heap manager environment variables are checked only once per activation group, at the first heap function which is called within the activation group. To ensure that the environment variables are used, set up the environment variables before the creation of the activation group.