Adding, changing, or removing filters can cause print requests still queued to be canceled. This is because the print service evaluates all print requests still queued to see which are affected by the filter change. Requests that are no longer printable, because a filter has been removed or changed are canceled (with notifications sent to the people who submitted them). There can also be delays in the responses to new or changed print requests when filters are changed, due to the many characteristics that must be evaluated for each print request still queued. These delays can become noticeable if there is a large number of requests that need to be filtered.
Because of this possible impact, we recommend making changes to filters during periods when the print service is idle.
``Defining a filter'' describes how you can write a filter.