Existence of multi-DB schema synchronizator

I need to know if there exists a tool that detects database schema (structure) differences between 2 databases and generates SQL scripts to alter 1 of them (the "target") according to the other (the "source").

Requisites:

• Multi-DB: ability to compare databases from Informix / SQL Server / Oracle servers. Example: compare an Informix schema with an Oracle schema.
• Offline working: must be capable to work without being connected to the servers (using SQL scripts as input).
• Check for differences in:
  • column names / types / nullability, etc.
  • Primary Key / Foreign Key / CHECK constraints (very important)
  • triggers
  • indexes
• Must not be ERwin nor Adept SQL