Cause : CU: Insufficient memory - comes when too many data sets are configured on this Control Unit. When encountering a "CU: Insufficient memory" error on a Siemens G120 drive, it typically indicates that the control unit (CU) of the drive doesn't have enough memory to perform the required operations.

This can happen due to various reasons, including a large program size, excessive data storage, or configuration settings that exceed the available memory. 

- reduce the number of data sets.