A direct link is a bilateral settlement arrangement connecting two CSD infrastructures. Under it, one depository maintains a position in the other’s system, allowing members of each depository to transact in securities recorded by the other. The depository providing access is known as the investor CSD, while the depository maintaining the relevant securities records is the issuer CSD.
Source: European Central Bank (ECB) (source). This glossary entry is an independently worded adaptation of the cited information.