There are a few 'gotchas' with Variables which are noted below. If you have any issues with Variables, please refer first to this section.

## Variable Value

A Variable's value field can only contain 63 characters or less. This is because Opsview Monitor cannot allow the service description to be longer than 128 characters​ when combined with the Service Check name. If it is longer, this will fail when running 'Apply Changes' in the Configuration menu, and the message below will be displayed:

As a Variable's value is used in the Service Check name, only certain characters are allowed for the value: alphanumerics, space, period, forward slash and hyphen. Any other characters will cause the UI to say "The value in this field is invalid".

To work around the character and length restrictions you can use the `Override Arg 1 ` field; this has no character restrictions and the field length is significantly larger. For the Servicecheck configuration you would then use `%VARIABLE:1%` instead of `%VARIABLE%`.

## Internally generated variables

Some Variables are internally-generated, so it is not necessary to manually add information at the Host edit pages. There is currently only one internally-generated variable:

Add the Host Template to this Host so that the appropriate Service Checks are created to monitor each variable.