Solves - "I wrote my app using the native MySQL API but the company is migrating to Oracle. I can tweak the queries to work with Oracle but I really don't want to have to modify the app to use OCI."
The SQL Relay Drop-In Replacement Libraries are shared-object libraries that can be LD_PRELOAD'ed to take the place of the native MySQL/MariaDB or PostgreSQL client libraries.
Many apps that were written to use MySQL/MariaDB or PostgreSQL dynamically load a client library to talk to the database.
The SQL Relay Drop-In Replacement Libraries intercept the native client library calls, map them to the SQL Relay equivalents and aim the client at an SQL Relay server.