DB2 start tuning needs privilege
@ Mark Barinstein many thanks to you because you made it easier for me

This worked with me with below two steps :-

1- [db2inst@localhost ~]$ db2 connect to TESTDB

2- [db2inst@localhost ~]$ db2 "CALL SYSPROC.SYSINSTALLOBJECTS('EXPLAIN', 'C', '', current_user)"