Graph Accumulator Properties

Use the Graph Accumulator Properties dialog box to create a graph item that represents the sum (or difference) of two or more other graph items.

For example, you may be graphing a router interface to measure the traffic into (ifInOctets) and out of (ifOutOctets) the interface. You could use the Accumulator properties to create a graph item that represents the sum of ifInOctets and ifOutOctets. This graph item would show you the full bandwidth on the interface.

1. Use the Items box to add (or subtract) two or more graph items. The current graph items are shown in the Legend below the graph. The first item is number 1, the second is number 2, and so on.

   In the Items box, click the plus (+) button. The Item list appears and shows the current graph items. Select an item and click OK. Then, click the plus or minus button again to add or subtract a second item. You can add or subtract more items in the same way.

2. Set any of the following options:
   • Absolute values. When selected, graphs the reported values of an SNMP  Simple Network Management Protocol is the protocol governing network management and monitoring of network devices and their functions. object rather than graphing the change between the last reported value and the current value (which is the default method). When graphing a counter, such as ifOutOctets, the reported values will continuously increase, so if you selected Absolute values, the graph will continue to "stair-step" up the scale. Counters are best graphed using the default method, which uses the change in value. Absolute values are appropriate for SNMP objects that have integer values, such as the number of FTP users on an FTP server.
   • AutoScale. When selected, the graph scale for the SNMP object is determined by the graphing utility. This is a relative scale that is calculated to make the graph fit into the vertical scale. If you turn off this option, the Scale option becomes active and you can enter a value to scale the graph.
   • Scale. When AutoScale is cleared (not checked), you can enter a fixed value in this text box to determine the scale of the graph. You may want to try different values in this box until you find a scale that is useful.
   • Bytes to Bits. When selected, it multiplies the value reported for the SNMP object by 8 to approximate the count in bits. This option can be used with SNMP objects that are counters, for example if you want to know the baud rate while monitoring a T1 router port, you want (ifOutOctets * 8) to give you a value close to the real baud rate.
   • Rate per second. When selected, it calculates the average change per second in the values reported for the SNMP object, and then graphs the result. To calculate this average, it takes the difference between the latest reported value and the previously reported value, then divides by the number of seconds between reported values. This is useful when the graph Interval is different than one second. You cannot use this option with the Absolute values option.
   • Reset values. When selected, it clears the values for the selected SNMP object when you exit the dialog box. You can clear the values for all SNMP objects on the graph, from the Edit menu, by selecting Clear.
   • Line width. Sets the width of the line that represents the selected SNMP object on the graph. Select a width from the list box.
   • Color. Sets the color of the line that represents the selected SNMP object on the graph. Select a color from the list box.
3. Click OK to add the item to the graph. This new graph item represents the combination of one or more graph items. In the Legend, the Object field for the item will show the list numbers of the graph items. For example, if the new item represents the sum of the first two items in the Legend, the Object field will show "+1+2" for the new item.