A service pack (SP) is a collection of patches, fixes and enhancements that upgrades a software package. Microsoft® is the most familiar example of a company that uses service packs to maintain its operating systems, but they are also used by other manufacturers of professional software packages.
Service packs are successively numbered, such as SP1, SP2 and so on, each augmenting the original software to act as a kind of version number. For example, one might be using XP® SP2, XP SP3, Vista®, or Vista SP1. First and third-party software designed to work with these operating systems often require installation of a particular service pack to be compatible.
A service pack can be cumulative or incremental. A cumulative service pack includes the contents of previously released service packs, so that if one wanted to upgrade from the original software package to the latest service pack, installation of previous packs would not be required. An incremental service pack does not contain previous fixes and enhancements, and requires the previous service pack(s) be installed beforehand, in the order of release. In some cases Microsoft refers to an incremental pack as a service release (SR).
Service packs make it easier to upgrade software because the entire pack can be downloaded and installed in one fell swoop, rather than having to download and install each individual fix or enhancement. Not only does this save time, it also reduces possible errors in the upgrade process. Between service pack releases, however, people are encouraged to keep operating systems up to date by patching them against security threats as patches become available. Luckily, this isn’t too difficult to do.
Microsoft has an automatic update feature that allows the operating system to poll for updates without user intervention. When found, they can be installed automatically or reviewed by the user first, according to system configuration. The second Tuesday of each month, known as Patch Tuesday, Microsoft releases security patches for many of its products, including its operating systems. If you prefer to manually check for updates or to enable manual updates only occasionally, checking on Patch Tuesday is a good idea.
In some cases, installing a newly released service pack might make the system unstable. It could contain enhancements that have not been tested in the wild and conflict with particular hardware and software configurations. The release of XP SP3 caused some computers to enter a cycle of spontaneous rebooting, among other problems, triggering much aggravation for users and Microsoft alike. To avoid taking chances, you can opt to keep the operating system patched monthly, but delay installing a newly released service pack until it’s clear there are no issues. You can also elect to not install a service pack at all, though future software releases might require it and it might contain security enhancements that are unavailable as separate patches.