Operating System Monitor Data: Memory Management (SAP Library

Operating System Monitor Data: Memory Management

Definition

The data that you can check in the operating system monitor for memory management includes data for the swap space and paging as well as the physically available memory. The following values are measured:

Physically available and free main memory in Kilobyte; the minimum and maximum free main memory are also measured hourly.

Note

As a rule of thumb, if CPU bottlenecks occur if there is less than 10 MB of free physical memory for a small hardware configuration. This value can vary depending on operating system and system size.

Paging is the exchange of data pages between the main memory of a host system and the overflow store in a paging file on the hard disk; paging occurs if the main memory is not large enough for the contexts of all running processes SAPOSCOL measures the number of pages paged in and paged out per second with the quantities of memory paged in and paged out in kilobytes.

High paging rates indicate that the main memory is too small for the running processes. Measures that you can take are to extend the main memory, to move processes to other host systems, and to delay memory-intensive program runs to times of lower system workload.

Note

On Windows platforms (unlike UNIX platforms), the system performs paging out as a precautionary measure even when space is not required in the working memory, meaning that this value is irrelevant and you should only consider the paging in rate. Under UNIX, on the other hand, Page_Out is the critical value for evaluating the paging.

Swap Space is storage space on the hard disk to which data that is not required is written from the main memory, so that there is space in the main memory for the program currently being executed. SAPOSCOL measures the configured and free swap space in kilobytes and the actual and maximum size of the swap space in kilobytes.

In addition, the maximum and minimum sizes of the free swap space is measured hourly. The most important values are the free and the actual swap space.

Note

Not all types of swap space are available on all operating systems. For this reason, in some cases, the actual swap space size corresponds to the configured and maximum swap space.

Use

The system displays the specified data when you call the operating system monitor.

In the detail data, the system also displays the performance history for the last 24 hours and 30 days (see also Detail Data of the Operating System Monitor).

To call the individual functions in the table, choose the Detail Analysis menu in the operating system monitor.

Function	Menu Path
Check memory usage for the last 24 hours	→ Goto → Current Data → Previous hours → Memory
Check the swap space usage for the last 24 hours	→ Goto → Current Data → Previous hours → Swap
Check paging and swap space for the previous days for one server	→ Goto → Performance Database → Compare recent days
Check paging and swap space for the previous days for various servers	→ Goto → Performance Database → Compare all servers

See also:

Operating System Monitor Data: CPU

Operating System Monitor Data: File System and LAN

Operating System Monitor and Operating System Collector SAPOSCOL initial pages.