Re: page_in values in vmstat output

Remember, page-ins are a normal part of program startup, and it could be normal. Your need to check the scan rate to be sure.

When an Oracle server begins to run low on RAM memory, the page stealing daemon process awakens and UNIX begins to treat the RAM memory as a sharable resource, moving memory frames to the swap disk with paging operations.

The page-stealing daemon operates in two modes. When RAM memory shortages are not critical, the daemon will steal small chunks of least-recently-used RAM memory from a program. As RAM resource demands continue to increase, the page-stealing daemon escalates and begins to page-out entire programs RAM regions. In short, we cannot always tell if the page-in operations that we see are normal housekeeping or a serious memory shortage unless we correlate the activity of the page stealing daemon with the page-in output.

To aid in this, the vmstat utility gives the sr column to designate the memory page scan rate. If we see the scan rate rising steadily, we will have hit the page-stealing daemon's first threshold, indicating that entire program's RAM memory regions are being paged-out to the swap disk. Received on Mon Feb 10 2003 - 16:53:37 CST