Evaluate all the updates to determine their applicability, and weigh the cost of deploying an update against the benefits. Plan the installation of applicable updates. If the update is scheduled inappropriately, it might make a computer or information resources unavailable when needed. If an update must be performed on a large number of computers, there can be a period of time when some computers on the network are using different and potentially incompatible versions of software, which might cause information loss or corruption. The update may introduce new vulnerabilities.
Updates can also cause a number of problems in other installed software.
You may want to consider running a previously developed regression test suite to compare current performance with past performance. Another approach is to install the update in an isolated test environment and run a series of user trials before releasing the update on your operational systems. A number of software packages exist that will tell you the differences to the system just prior to and after installing the update. We recommend that you use one of these to fully understand and analyze the effects of the update on your systems. In addition, you should always backup your system prior to applying any updates.