I'm using MySQL on Linux with the latest version of nwnx_odbc for Linux.
General suggestions if you're storing a lot of data:
- use MySQL or PostgreSQL
- create custom tables with the structure you need and use custom queries to manipulate only the data you need
- create indexes on fields you use for selection
- check for nested loops with queries (those can usually be optimized by using joins for SELECT queries or batching for updates/deletes).
- batch inserts/replaces when you insert more than 100 rows