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
18.7: Tuning Memory
18.7 Tuning Memory
If you have determined that the memory resource is a performance bottle-neck, and you have considered load-balancing options, the next step is to tune the memory subsystem.
18.7.1 Introduction
VAX systems typically have between 4 and 512 MB of physical memory. OpenVMS allocates memory in pages of 512 bytes each. You can translate megabytes to pages by multiplying by 2,048. For example, a system with 16 MB of memory has approximately 32,000 pages. With the introduction of OpenVMS 6.0, OpenVMS supports up to 3.5 GB of physical memory on the VAX 6600, 7600, and 10000 systems.
OpenVMS/Alpha systems use a different page size than OpenVMS/ VAX systems. An Alpha page size can be either 8K, 16K, 32K, or 64K, however, all current systems use an 8K page. To maintain compatibility with VAX systems, Alpha systems define a unit of page measurement called a pagelet, which equals one VAX page. For example, on an Alpha system with an 8K page, 1 Alpha page equals 16 pagelets.
On an Alpha system, usually all references to a quantity of pages are displayed and evaluated in both of pagelets and pages (e.g., GBLPAGES, PGFLQUOTA), for instance:
$ <b class="bold">mcr sysgen</b> SYSGEN> <b class="bold">SHOW GBLPAGES</b> Parameter Name Current Default Min. Max. Unit Dynamic -------------- ...
Copyright Lawrence L. Baldwin, Jr. 2004 under license agreement with Books24x7
