If your system is offsite or you’re working remotely, just type DSPPTF. The first value (##MACH#A or ##MACH#B) indicates the copy of Licensed Internal Code that the system is currently
Look at your display panel on the server. It will show either A or B. That will tell you what side you’re running from.
Here’s some IBM info on this topic.
The system maintains two copies of all Licensed Internal Code on the system. One copy is considered the permanent copy and is stored on system storage area A. The other copy is considered the temporary copy and is stored on system storage area B. When the system is running, it uses the copy that was selected before the last IPL (initial program load).
System storage areas A and B
A B in the Data display on the front panel of the system unit indicates that the next system IPL will be made from the B or temporary storage area. The B storage area contains any Licensed Internal Code fixes that have been temporarily or permanently applied. Temporarily applied Licensed Internal Code fixes can be applied permanently (copied to the A storage area) or be permanently removed.
For the system to use the latest Licensed Internal Code fixes that are temporarily applied, you must be using the B storage area. The B storage area is what you normally use. Select the A storage area if the IPL to the B storage area fails because of a temporarily applied Licensed Internal Code fix.