proc mydrc { handle } { }
The DRC function could be any Tcl code that checks your parameters for correctness. The DRC procedures can access (read-only) the Platform Specification Format database (which the tool builds using the hardware (XSA) and software (MSS) database files) to read the parameter values that you set. The handle is associated with the current library in the database. The DRC procedure can get the OS and library parameters from this handle. It can also get any other parameter from the database by first requesting a handle and using the handle to get the parameters.
For errors, DRC procedures call the Tcl error command error "error msg" that displays in an error page.
For warnings, DRC procedures return a string value that can be printed on the console.
On success, DRC procedures return without any value.