It´s higly recommended to encrypt local replicas of Domino Databases. But in some situations you could have the need to decrypt those local replicas ( e.g. when an employee creates local archives and you have to access the data inside the archive database ).
Then you can either use an agent with LotusScript to decrypt the database ( which is described here: LINK ) or you also can use a tool to decrypt all databases in a folder or the whole DATA directory which have been encrypted with the same User ID.
So for example: if all databases have been encrypted with the User ID “John Doe/ACME” then you have to use this ID to decrypt the databases.
IMPORTANT:
** This tool is run from the Notes client only (32 bit application). This tool cannot be customized any further. This is an UNSUPPORTED tool with no warranties. Use at your own risk.
How to use this tool:
1) Download and place the file “DisableEncDbsX86.exe”in the Notes program directory (Example C:\HCL\Notes). If you have troubles downloading the file please contact me
2) Open command prompt and switch to the Notes program directory:

3) To run the decryption tool against the Notes\Data directory use the below command and provide password for Notes ID file which was used to encrypt the databases. If you don’t have the User ID you simply can extract it from the hopefully configured ID Vault 😉
DisableEncDbsX86.exe “” “”

This will decrypt ALL encrypted databases in your Notes\Data directory.
If you want to run the decryption tool against a single database first move the database for example to the directory “2decrypt” and afterwards run the following command:
DisableEncDbsX86.exe “” 2decrypt
Hopefully you never have to use it but maybe you need this tool one time.