Starting with Liferay DXP 7.3 SP3+ and 7.4 GA1+, Liferay adopted a new release model for delivering updates and fixes. This new approach is referred to as Bundle Releases and replaces the previous model of providing partial updates in the form of fix packs and service packs. This improves security by providing customers not only with the latest Liferay DXP updates, but also the latest versions of Tomcat and other libraries in each release.
An essential part of maintaining your installation is backing it up. Please see Backing Up for details on the system components to save regularly.