Thousands and sometimes millions of lines of code need to be examined to determine if there is a problem. A typical inventory application, for example, might require 10,000 working hours to scrutinize and fix. In terms of job size, fixing PC application problems is typically a small task. The number of PCs at a given site often multiplies the verification process into a massive undertaking, however. With PCs, applications are usually located on each PC, even in networked settings.
Someone needs to track down and fix every affected application.
Databases are another common area for Y2K problems. Most databases are Y2K-compliant, but some older or poorly supported databases aren't. What's more, custom databases created within organizations might not have been designed to handle post-1999 dates. Those databases, along with the applications that access them, must be tested. While not as common, Y2K issues can arise within operating systems.