The incremental design-rule checker is always running, examining your work, and issuing error messages when an error is detected.

To control the DRC, use the "DRC" preferences (in menu File / Preferences..., "Tools" section, "DRC" tab).

By default, the incremental design-rule checker is on. To turn it off, uncheck the "On" checkbox in the "Incremental DRC" section.

MOS contact nodes automatically increase the number of cuts when they grow larger (see Section 7-4-1). Because of this, very large contact nodes can create excessive work for the design-rule checker as it examines each of the cuts. To save time, check the "Ignore center cuts in large contacts" check box, which will examine only the cut layers around the edges of contact nodes.

After analysis of the circuit, you can review the errors by typing ">" and "<" to step to the next and previous error that was found. You can also see a list of errors in the Cell Explorer (see Section 4-8).