There are more than 10,000 system messages, and when they are output, you typically only ever receive a system message code with some numeric or alphanumeric data following the system message code to provide more information about the system message code specifics. Before attempting to troubleshoot a system message, you need to determine the meaning of the system message.
Using the Error Lookup command, you can often do that without ever needing to open a book.
> ERR <code>
Note: Leading zeroes are not required when entering the numeric value of a system message. Example: DTA021 is output. In the Software Input Output Reference – System Messages guide, the system message is in the format DTA0021 (for sorting purposes), but when typed in to the SL1 interface, the preceding zeroes are not required.
> ERR DTA21
Works just as well as:
> ERR DTA021
And both should output:
DTA0021 loop Frame alignment alarm persisted for 3 seconds.
In some cases (I’ve not figured out all of them, but I think it has to do with available memory), the message will not output, in which case you have to crack the books open.