LOAD cannot executed via CLI because it's a "Command Line Processor Command". See http://publib.boulder.ibm.com/infocenter/db2help/topic/com.ibm.db2.udb.doc/core/r0010410.htm for a list. These commands are resolved by the command line processor ("db2" or "db2.exe"), not the database engine. You may get some of the functionality on C level, but not with CLI SQL.

Do a system() instead.

system('db2', 'LOAD from ...');
if ($? == 0) {
  # all ok
} if ($? & 1) {
  # oops, we didn't select at all?
} if ($? & 2) {
  # just a warning
} if ($? & 4) {
  # execution failed
} if ($? & 8) {
  # command line processor failed
} if ($? & ! 15) {
  # what?
}
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