OpenVMS System Management Guide, 2nd Edition
This complete text details the tools, technologies and techniques that can configure, maintain, and tune computers running Hewlett-Packard's high-performance OpenVMS operating system.
TABLE OF CONTENTS OpenVMS System Management Guide, 2nd Edition
18.5: Identifying Resource Dependencies
18.5 Identifying Resource Dependencies
After you identify a performance problem, you have to decide which system resource to focus on. Ideally, you should focus on the resource for which users spend most of their time waiting. The procedures for roughly estimating CPU, memory, and disk dependency from the usage statistics that you have collected are discussed in the following sections.
18.5.1 Estimating Memory Dependency
Available memory on an OpenVMS system is organized as a linked list of pages known as the free-page list. When a process requests memory, pages are removed from the head of the free list and assigned to the process.
Each process has an associated working-set list that specifies the pages of memory resident in physical memory and that the process can immediately access. The maximum size of the working-set list of a process is generally configured with AUTHORIZE parameters (e.g., WSQUOTA, WSEXTENT). By restricting working-set sizes to a few hundred or a few thousand pages, you can ensure that no one process consumes all the physical memory of a system.
When a process attempts to access more pages of memory than its working-set list will allow, page replacement occurs. Replacement involves removing older pages from the working set and replacing them with the newly accessed pages. When a page containing read-only structures (e.g., executable code) is replaced, it is placed at the end of the free list. Replaced pages are likely to remain on the free-page list for some time before being allocated for...
Copyright Lawrence L. Baldwin, Jr. 2004 under license agreement with Books24x7
