How do you find the size of a client

Goto transaction SCCL
give the source client (which you have to find size)
and the target client
then check test run
at the end you will see the size of client

How to view Locked Transaction codes

Goto transaction se11 or se16 and view the table TSTC, the field is CINFO. Enter "A0" as the "HEX01 data element for SYST" starting value and "A9" as the ending value. Instead of doing such cumbersome viewing of table, you can run ABAP report rsauditc to view locked transactions. Use t-code sm01 to lock/unlock the codes