I'm sure others can answer better than I. But back in the the 1980s, when I was programming in Natural and in COBOL pgms that ran against an Adabas database, it was said that Adabas was the best (most efficient) DBMS on the market. Almost all serious computing was on mainframes in those days.
BTW: Some guy was caught at some airport with a tape that contained the source code for Adabas, back in those days. He was going to sell it to the Soviets, who were in the black (or should I say "red?") market for it. Software AG used this incident in a magazine advertisement, showing the top Russian leaders, with their fur hats on, on what was probably the traditional May Day reviewing stand, wherein they stood and watched the Soviet military parade. Someone put this ad on the bulletin board where I worked, and someone (else?) wrote on it in pen, "They can have ours for free!" Probably not a well thought out complaint, if the claim is true that Adabas is or was the best database.
BTW2: It looks like the gov't/security/defense sector of the US economy is moving first, ahead of any private sector recovery. My experience with consulting firms and job boards is that things like Adabas and Unysis are in many gov't shops. This includes, BTW, NASA! This is the motivation behind my other post, today.