Dmitry, although there is support for ObjectScript (needed for object DB and graph-style applications), I think most migrations would simply use SQL and Embedded Python.. both fully supported by IRIS. It's possible you are thinking of the 'Cache' database product that preceded IRIS.
Good info, Irene. Regarding MSSQL (and Sybase SQL), it is also possible to set the shell to process Transact-SQL instead of IRIS SQL.
I'm a new-ish employee at Intersystems and have attained SQL certs for Snowflake, Vertica, and SQL_Server in the past. I have a strong interest in db certifications and would like to contribute if I can.