Special Features under Windows NT for Memory Management

• The Windows NT file cache directly competes with R/3 programs and pushes these programs out of the working memory. Unlike UNIX, the file cache is only indirectly influenced by a switch in the network setting.
• Writing and reading R/3 roll and paging blocks in the relevant storage files extends the Windows NT file cache and pushes out the R/3 programs from the working memory.
• Copying roll and paging blocks when changing contexts is more time-consuming than including memory blocks when using Extended Memory. Extended Memory also has the advantage that it is subject to the performance-oriented Windows NT paging mechanism.
• Windows NT does not offer you code sharing (exception: DLLs). This means that all work processes fill the complete memory area in the memory. This leads to a greater memory requirement for the work processes compared to UNIX.
• Pages in the Extended Memory that are not in the address area of an active process are transferred automatically in the page file by the operating system. The pages remain duplicated in the physical memory until the memory area is required by another process. They are marked as transferred. The transfer has a low priority and is described as a lazy page out. If a work process now accesses a lazy page out, the memory area is included again without the page file access. If there is enough working memory, the result is a large [page out] and a small [page in] value. When a lazy page out action occurs, Windows NT creates permanently free available working memory. Therefore, even a page-in with a page file access is faster than on UNIX systems, since it is not necessary to transfer another page beforehand (no direct page-out before a page-in).