Some hosts have MEDLINE split into multiple files while other hosts consolidate all of the MEDLINE data under the MEDLINE name. When split, the common method of splitting the data can be described as: MEDLINE (1966-present) and OLDMEDLINE (1949-1965). The coverage of OLDMEDLINE era records (1949-65) is specifically sourced from two printed indexes: the Cumulated Index Medicus (CIM) and the Current List of Medical Literature (CIML).
MEDLINE is carried by many hosts and search systems, since it is a publicly available database. While there are many free to use systems such as PubMed, for-pay systems such as EBSCOhost, Dialog, STN, and Ovid also host MEDLINE. These systems each offer their proprietary search capabilities to add value to MEDLINE. EBSCOhost also hosts a full text version of MEDLINE which includes full text articles for a fraction of the records present. Not to be outdone, the free PubMed offers links to an even greater fraction of full text articles (but does not actually host the full text articles, unlike EBSCOhost).