This page explains the differences between the terms 'updating', 'upgrading', and 'migrating', as it relates to Drupal core, so that you know where to go next depending on what you want to do.Note: For updating/upgrading Drupal modules and themes, Jump down to the 'modules and themes' help-box below.Upgrade: Switching from Drupal 6 to Drupal 7, or from Drupal 6 to Drupal 8, or from Drupal 7 to Drupal 8 is an 'upgrade'.
When trying to do a manual update of the definitions, the progress says "Searching" and goes to about 25%.
At this point, it stalls, for quite a while, and then fails.
If that is what you want, go here: Backing up and migrating a site The process of 'upgrading' your site from one major version to another also involves elements of 'migrating', but if you are 'upgrading' just go to the link previously mentioned: Upgrade to Drupal 7 or 8 - Major version change to your current D6 or D7 site Beginners Choosing Drupal version (This link opens in a new tab/window.) That page details, among other things: an explanation of the use of Drupal versioning numbers; how you can determine what version your site is using; and things for you to consider when deciding whether or not to upgrade your site at this time.
⤵ Strictly speaking, 'updating' refers to taking your site from one 'minor' version to another, as for example, from Drupal 7 version d7.1, to d7.2; or from Drupal 8 version d8.0.0 to d8.1.3, etc.
No matter which version your site is currently using, you can update to the latest minor version that is available.