There are two different \\\"magnitudes\\\" of upgrades. There are major upgrades and minor updates. A major upgrade updates Drupal from one major version. Because major Drupal versions indicate substantial changes, such upgrades are often time consuming, requiring many steps both before and after the actual installation of the software.
Minor updates move from one point release to another newer point release. A point release is a software update that contains only bug fixes and minor feature changes. Its major version number remains the same, but its minor version (its point number) is incremented.
Drupal\\\'s current major version number is 7, and its minor version number (as of time of writing) is 12, so we have version 7.12. Updating minor releases is much simpler than major upgrades, and should also be done regularly. Since most minor versions are released for security or stability reasons, they are typically quite important. In this section, we will look at updating Drupal multi-site configurations. The process differs from upgrading a single-site instance in that there are more steps, and the order of steps must be done carefully. Since a multi-site runs only one copy of Drupal, all of the sites on a multi-site install must be updated at the same time. Multi-site updates differ from single-site updates in one crucial way: while Drupal\\\'s code needs to be updated only once, each individual site needs to go through the updating process. To keep site impact to a minimum (and to avoid catastrophes), doing these updates requires a special process.