This is to allow the cutover from the old to new servers, previously attempted and aborted on March 25th due to undocumented application conflicts, to take place. The downtime is currently scheduled to be 8 a.m. - 1 p.m., although the anticipated downtime may be shorter than that window.
The new servers should improve the catalog response times as well as the general performance.
We apologize for any inconvenience this outage may cause. During the outage you may want to consider using WorldCat as an alternative, as it indicates with fairly high reliability whether we have a title. Note, however, that the library is closed on Sunday morning, so there is no access to our print collections during this outage.