Want to merge two organisations with a third party application

Merging two organisations is always a painful process, and you should be weary of couple of things and plan for them accordingly.

Object metadata - is it exactly the same? Especially around the fields that have the same name but have different semantics in each org.

Validation/Workflow rules - Does a workflow rule in one org conflict with another workflow rule in the other org.

Division is used to segment your data into different logical groups. The user will then have access to the data that belongs to the division that he is assigned to. If you do not have an existing role hierarchy to contend with, Divisions should work fine.

The following caveats apply to division though:

It is not recommended if data is shared across divisions
Shared accounts and shared opps cannot be assigned to more than one division
Each user can have only one default division. if you have numerous users that would own data in several divisions then divisions are not recommended.
Also, if security is a big concern, then you are out of luck, because users can always view records in all divisions. They do not provide the type of security that role hierarchy provides. Most importantly, if the Division field is added to their page layout, they can create records in other divisions.
Orphan records are automatically assigned to your "global" division
Records w/o parents that are created via the Force.com API are the given the default division of the API user who created them.
If you wish to use the Quotes feature in Salesforce.com, Divisions cannot be enabled. If Divisions was previously enabled, Quotes cannot be enabled.

Hi,

But what if the record types are also same??