OpenVMS Record Management Services to Linux Replacement Recommendations

Question

I am currently trying to find recommendations on how to migrate from OpenVMS RMS to Linux. Legacy code makes use of Indexed and Relative files. I currently have some ideas on how to move away from RMS and these include: Unix GDBM, Relational database (least likely to take this approach due to reluctance of adding this large of a complexity to the current project, and loading files into memory and working with them that way.

My question is if anyone has had any experience with this and if they are able to recommend a solution?