There are three ways to move transports from one system to another.
1. Moving the transport files form the directories “data” and “cofiles” manually.
When the transport is released in the source system SAP automatically puts the transport files into the transport directory on file system. This files easily can be copied to the second system an be imported via transaction “STMS”.
2. Using CAR files
CAR files are packed files like a zip file. The contain the data and cofiles.
car.exe -cvf packedFile.car data\R900000.XXX cofiles\K900000.XXX
(car.exe is a SAP standard tool, XXX is the system ID)
This CAR files can be imported via transaction SAINT. This allows import files from frontend into the data and cofiles directory without direct access to the file system. After importing the file via SAINT the transport can be imported using STMS. This is be the common way to transport software to other systems outside the current landscape.
3. Using SAR and PAT files
These files are more special. They allow to install software as Add-On in SAP. This is required if the program should be certified by SAP. They have to be created using the AAK (SAP Add-On Assembly Kit). Unfortunately, I have not created this files myself yet. But it seems to be very complex to get this running, because there are some checks which have to be passed. The files can be imported via transaction SPAM (upload) and SAINT (import).