Name & is invalid

What causes this issue?

The current name does not ahere to the naming conventions.
Names for InfoSets and queries can be a maximum of thirty charachters
long, and must contain only letters, numbers, and underscores ( _ ). A
name can also begin with a namespace prefix.
A namesapce prefix is a maximum of ten characters long, and starts and
ends with a forward slash (/).

System Response

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

How to fix this error?

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.