You are confused. You are using DB2 for z/OS and obviously looking at manuals for DB2 for Linux, UNIX, and Windows. These are 2 different products. The 'db2 -x' is for Linux, UNIX, and Windows command lines.
You might want to see if you can find the ISPF panel for SPUFI (probably on the DB2 ISPF menu).
Or you can use DB2 Connect to access DB2 for z/OS from your workstation, in which case you can use the DB2 for Linux, UNIX, and Windows commands.