Memory Monitor

The SiteScope Memory Monitor provides an easy way for you to track how much virtual memory is currently in use on your server. Running out of memory can cause server applications to fail and excessive paging can have a drastic effect on performance.

Each time the Memory Monitor runs, it returns a status message and writes it in the monitoring log file.

Usage Guidelines

What to monitor

One of the primary factors that can affect your Web server's performance is memory. The two most important measurements to detect problems in this area are Pages per Second and Percentage of Virtual Memory Used, both monitored by the SiteScope Memory Monitor.

About scheduling this monitor

In most environments, the Memory Monitor does not put a heavy load on your server. For monitoring remote UNIX servers, SiteScope will usually need to open a telnet or SSH connection to the remote server. While the monitor actions generally do not load the either server, managing a large number of remote connections can results in some performance problems. You use the error and warning thresholds to have SiteScope notify you if memory on a remote server starts to get low.

Common Problems and Solutions

Pages per second measures the number of virtual memory pages that are moved between main memory and disk storage. If this number is consistently high (>10 pages/sec), system performance is being affected. One solution is to add more memory. Another solution is to turn off non-critical services that are using memory, or move these services to a different machine. The SiteScope Service Monitor measures the memory usage for each service.

Percentage of Virtual Memory Used measures the percentage of memory and paging file space used. If this number reaches 100%, services that are running may fail and new ones will not be able to start. Increasing the size of the paging file may solve the immediate problem but may decrease performance by increasing paging. A slow increase in Virtual Memory Used is often caused by a memory leak in a service. The SiteScope Process Detail tool (available when you click the tools link listed in the Monitor Detail Table) can be used to view the memory used by each service. The ideal solution is to install an upgraded version of the service without the leak. An interim solution is to use the SiteScope Service Monitor to measure the service size and invoke a SiteScope Script alert to restart the service when it becomes too large. If restarting the service does not fix the leak, it may be necessary to add a SiteScope Script alert to restart the server when memory usage is too high.

Completing the Memory Monitor Form

To display the Memory Monitor Form, either click the Edit link for an existing Memory Monitor in a monitor table, or click the Add a new Monitor to this Group link on a group's detail page and choose the Add Memory Monitor link.

Complete the items on the Memory Monitor Form as follows. When the required items are complete, click the Update Monitor button.

Server: Choose the server that you want to monitor. The default is to monitor memory on the server on which SiteScope is installed. Click the choose server link to monitors memory on another server.
Update every: Select how often the monitor should check this drive. The default interval is to run or update the monitor once every 10 minutes. Use the drop-down list to the right of the text box to specify another update interval in increments of seconds, minutes, hours, or days. The update interval must be 15 seconds or longer.
Title: Enter a title text for this monitor. This text is displayed in the group detail page, in report titles, and other places in the SiteScope interface. If you do not enter a title text, SiteScope will create a title based on the host, server, or URL being monitored.

Advanced Options

The Advanced Options section presents a number of ways to customize monitor behavior and display. Use this section to customize error and warning thresholds, disable the monitor, set monitor-to-monitor dependencies, customize display options, and enter other monitor specific settings required for special infrastructure environments. The options for this monitor type are described below. Complete the entries as needed and click the Add or Update button to save the settings.

Disable

Check this box to temporarily disable this monitor and any associated alerts. To enable the monitor again, clear the box.

Verify Error

Check this box if you want SiteScope to automatically run this monitor again when it detects an error.

Update Every (on error)

You use this option to set a new monitoring interval for monitors that have registered an error condition. For example, you may want SiteScope to monitor this item every 10 minutes normally, but as often as every 2 minutes if an error has been detected. Note that this increased scheduling will also affect the number of alerts generated by this monitor.

Schedule

By default, SiteScope monitors are enabled every day of the week. You may, however, schedule your monitors to run only on certain days or on a fixed schedule. Click the Edit schedule link to create or edit a monitor schedule. For more information about working with monitor schedules, see the section on Schedule Preferences for Monitoring.

Monitor Description

Enter additional information about this monitor. The Monitor Description can include HTML tags such as the <BR> <HR>, and <B> tags to control display format and style. The description will appear on the Monitor Detail page.

Report Description

Enter an optional description for this monitor that will make it easier to understand what the monitor does. For example, network traffic or main server response time. This description will be displayed on with each bar chart and graph in Management Reports and appended to the tool-tip displayed when you pass the mouse cursor over the status icon for this monitor on the monitor detail page.

Depends On

To make the running of this monitor dependent on the status of another monitor or monitor group, use the drop-down list to select the monitor on which this monitor is dependent. Select None to remove any dependency.

Depends Condition

If you choose to make the running of this monitor dependent on the status of another monitor, select the status condition that the other monitor or monitor group should have in order for the current monitor to run normally. The current monitor will be run normally as long as the monitor on which it depends reports the condition selected in this option.

List Order

By default, new monitors are listed last on the Monitor Detail page. You may use this drop-down list to choose a different placement for this monitor.

Error if

Set the Error threshold for this monitor. By default SiteScope reports an error condition if memory use is more than 80%. You can change this to report errors based upon pages/second, Megabytes free, and percentage of memory in use. Choose the option you want from the drop-down list, select a comparison value symbol, and enter a threshold value.

For example, if you want SiteScope to report an error condition if your memory use is more than 96%, you need to choose percent used from the drop-down list, select >= from the comparison value list, and then enter 96 in the text box.

Warning if

Set the warning threshold for this monitor. By default SiteScope reports a warning condition if your memory use is more than 90% full, but less than the error threshold. You can change this threshold or set it to generate a warning based upon pages per second, Megabytes free, or percentage of memory in use. You must enter a whole number.

For example, if you want to change the warning threshold to 50%, choose percent used from the drop-down list, select >= from the comparison value list, and enter 50 in the test entry box.

Good if

You may also specify a threshold for a good reading. You may base it on pages per second, Megabytes free, or percentage of memory in use.