What happens to imported contributions?

Hey development gurus,

I am wondering how an organization functions when contributions are being imported, or have been imported in the past. Here are some of my concerns:

• Once those contributions are imported, can they be transacted upon?
• If so, are there steps to be taken to prevent this from happening, or catch it when it does?
• Are contributions imported into funds that are also in use for tessitura-originated contributions, or are the funds being imported entirely separate from those in use for tessitura-originated contributions?
• Is anyone doing contribution imports where it is totally kosher to make alterations to the contribution in Tessitura after the import? I would be interested to hear how this works out from the finance perspective.
• If there is an ID number associated with the contribution from an external system, is that ID number stored anywhere in Tessitura after the import? Contribution custom data, perhaps?