If I am understanding the question correctly, ALM has a three-tier architecture.

In a two-tier architecture, the client would work directly with the database.

In a three-tier architecture, the client communicates with an application server and the application server communicates with the database

2 and 3 tiered application example
https://www.screencast.com/t/hQi3i99rV5gv

Since ALM utilizes clients (ex. the ALM Desktop Client and Site Administration), An application server, and a database server, and the repository can also be on a server different from the application it is built on a 3 tier application architecture. The image linked below is from the installation and upgrade guide page 13 (also linked below) and shows the different tiers.

https://www.screencast.com/t/PWt0FsEw6sO

ALM Installation and upgrade guide
https://admhelp.microfocus.com/alm/en/15.5-15.5.1/pdfs/Install_Windows.pdf