Identify the current version/level of DB2 z/OS via an SQL statement

After the database has been upgraded to DB2 12, you can use the below SQLs to identify the current level:

select catalog_level from sysibm.sysdummy1;                   
---------+---------+---------+---------+---------+---------+--
CATALOG_LEVEL                                                 
---------+---------+---------+---------+---------+---------+--
V12R1M500                                                     
DSNE610I NUMBER OF ROWS DISPLAYED IS 1                        
DSNE616I STATEMENT EXECUTION WAS SUCCESSFUL, SQLCODE IS 100   
---------+---------+---------+---------+---------+---------+--

Another option:

SELECT GETVARIABLE('SYSIBM.VERSION') FROM SYSIBM.SYSDUMMY1    
---------+---------+---------+---------+---------+---------+--
                                                              
---------+---------+---------+---------+---------+---------+--
DSN12010                                                      
DSNE610I NUMBER OF ROWS DISPLAYED IS 1                        
DSNE616I STATEMENT EXECUTION WAS SUCCESSFUL, SQLCODE IS 100