GSE1015N A spatial reference system named "NAD83_SRS_1" does not exist
I just realized that there was a bug when I enable the databases to support spatial function.

db2se enable_db sample


While running this command line, it was interupted, but DB2 still reports that it successfully enabled the spatial function. Actually, this command takes very long to finish (more than 5 mins in my case), which makes me thought it gets stuck and interupt it with Ctrl+C. So the solution is just to wait until it finish without touching any keyboard.