MS Access and MS SQL server do not run on linux ... You would need to convert any MS Access or MS SQL Server database to something else (
MySQL,
PostgreSQL,
FireBird,
Sybase) to use it on Linux ... and develope a front end to use the database.
Oracle Databases (>8.1.7.x, 9.0.x.x, 9.2.0.x, 10g) run great on supported versions of Linux {like
RHEL (AS or ES) or
SLES (8 or 9)}... You can use
WhiteboxEL,
CentOS or
TaoLinux as a free substitute for RHEL. If you have an Oracle database versions (8.1.7.x, 9.0.x.x, or 9.2.0.x, 10g), you should be able to export it on the current platform and import it on your Linux platform.
IBM DB2 also runs on Linux as well.
Obviuosly DB2 and Oracle are expensive ... the others are free.