Each SMS Service has an Incoming SMS Fail Limit which you can configure on the SMS Service Form. This property allows you to define when Geo SCADA Expert will generate an alarm associated with an SMS service receiving invalid SMS messages.
The Incoming SMS Fail Limit works in conjunction with an internal Fail count which starts at 0 and increases by 1 each time an invalid SMS message is received. It is reset to 0 each time a valid SMS message is received or when a manual reset is triggered (see Checking and Resetting the Fail Count for an SMS Service). If the Fail count exceeds the Incoming SMS Fail Limit, an alarm is raised.
An SMS message is deemed to be invalid if:
- The SMS message received by the Pager Driver has an invalid structure. SMS messages consist of a variety of components, including protocol information, a time stamp, and the body of the message. If an SMS message does not contain the required components of a valid message, the Pager Driver will not process the message and will instruct Geo SCADA Expert to increase the Fail count will rise by 1.
- Geo SCADA Expert has received a message that has valid SMS components (as detected by the Pager Driver) but Geo SCADA Expert is unable to preform the command. Geo SCADA Expert cannot perform SMS commands if it is unable to match the database item and method (or command alias) defined in SMS message to a corresponding item and method in the database. This may occur when a user has made a mistake when entering the command in the body of the SMS message, for example, they may make an error when entering the name of a command alias.
Example:
The Incoming SMS Fail Limit is set to the default of 5 and the Fail count for SMS messages is at 0.
An SMS message with a valid structure is sent to the system. The Pager Driver analyzes the message, and having recognized that it is a valid SMS message, it extracts some of the information in the message and sends that information to Geo SCADA Expert.
Geo SCADA Expert receives the SMS message information from the Pager Driver. The information includes the body of the SMS message which contains a command alias. Geo SCADA Expert attempts to match the command alias with the configured command alias setting of a Method Call in the database. There are no Method Calls with matching command aliases and so Geo SCADA Expert cannot process the SMS message. This causes the Fail count to rise by 1.
The next 2 SMS messages to be received by Geo SCADA Expert are similar - they both contain invalid aliases. This causes the Fail count to rise by a further 2, so the count is now 3.
A valid SMS message is the next message received, and as Geo SCADA Expert can process the message correctly, the Fail count is reset to 0.
The next 5 messages have invalid structures and so are disregarded by the Pager Driver. The Fail count increases to 5, but there is no alarm yet as the Incoming SMS Fail Limit has only been reached, not exceeded.
The next SMS message to be received has an invalid alias and so cannot be processed. This causes the Fail count to rise to 6. As this exceeds the Incoming SMS Fail Limit of 5, an alarm is raised.
If the Pager Driver receives a signal that does not contain any SMS message components (for example, some other form of unsolicited signal), the signal is disregarded. This will have no effect on the Fail count as the signal was not identified as an SMS message.
To define the Incoming SMS Fail Limit for an SMS Service:
- Display the Pager Service Form.
- Select the SMS Service tab.
- Enter the Incoming SMS Fail Limit that you require. The Incoming SMS Fail Limit is set to 5 by default which is appropriate for many systems.
- Save the configuration.