This message is generated when the number of independent variables does not match the number of arguments in the solution function in the specification of the equations.
Off[message] switches off the message; On[message] switches it on. For example: Off[DSolve::derlen].
Examples
Basic Examples(1)
Three variables are specified in the third argument, suggesting that the input may represent a partial differential equation:
Avoid the error message by specifying only x in the third argument: