Starting in autumn 2018 I have been developing StrongDBMS (strongdbms.com, Twitter #StrongDBMS) which incorporates many of PyrrhoDB's ideas, but handles concurrency better than other DBMS I have managed to test. The reasons and source code are written up in GitHub, see shareabledata.org .These tests also showed up some weaknesses in Pyrrho.
Both Strong and Pyrrho use a minimal set of locks to manage concurrency and ensure ACID properties: one lock is for the DBMS itself, and one for each database file. Unfortunately, in versions up to 6.3, Pyrrho transactions can involve more than one database, and the database is stored in a sequence of files (with file names including sequence numbers 001 etc if required). Both of these "improvements" in Pyrrho make verification of ACID properties more difficult.
I will produce a cleaned up version 7 of Pyrrho that will be backwards compatible with Pyrrho 6.3, apart from lacking multi-database connections and supporting only one file per database.
