Hi,
what do you mean by IBM Mainframe? IBM has 5 "mainframe" databases:
- db2 for zOs on zSeries
- db2 for VSE AND VM on zSeries
- db2 for zLinux on zSeries
- db2 for iSeries on iSeries
But bear in mind that there is not all functionalities supported on all of this databases. Only db2 for zLinux is equal to DB2 Windows/Linux/Unix databases all other has somekind of limitations.
Migration is manly dependent on what you have already at database site? Tables, store procedures, triggers, etc. More you have on Oracle more problems can be expacted.
Please also see links provided at (search 'migration'):
http://dbforums.com/showthread.php?t=506495
Hope this helps,
Grofaty