Key Changes:

1. Synchronization and Atomic Counters:
   
   • Added dbLock to synchronize access to the database.
   • Added activeStatements to track active SQL statements.
2. Synchronization in Methods:
   
   • Wrapped database operations within synchronized (dbLock) blocks.
   • Used activeStatements.incrementAndGet() and activeStatements.decrementAndGet() to track active SQL statements.
3. Waiting Mechanism in vacuumDatabase:
   
   • Ensured vacuumDatabase waits until no other SQL statements are in progress before proceeding with the VACUUM operation.

This ensures that the VACUUM command only runs when it's safe to do so, avoiding the SQLITE_ERROR.