It is described here the way DataparkSearch processes different HTTP codes. Pseudo-language is used here for explanation.
200 OK
If -m command line argument ("force reindex") specified, GOTO 4.
Comparing new checksum with old one stored in database
If checksum are the same, next_index_time=Now()+Period, GOTO 7
Parsing the document, creating word list and adding in "url" table all of the found HREFs
Comparing created word list with old one stored in "dict" table
Doing UPDATEs, DELETEs or INSERTs in table "dict" if something is different in word lists.
Done
304 Not Modified
next_index_time=now()+Period
Done
301 Moved Permanently
302 Moved Temporarily
303 See Other
Deleting all words in table "dict" for current URL
next_index_time=Now()+Period
Adding an URL given in Location: header
Done
300 Multiple Choices
305 Use Proxy (proxy redirect)
400 Bad Request
401 Unauthorized
402 Payment Required
403 Forbidden
404 Not found
405 Method Not Allowed
406 Not Acceptable
407 Proxy Authentication Required
408 Request Timeout
409 Conflict
410 Gone
411 Length Required
412 Precondition Failed
413 Request Entity Too Large
414 Request-URI Too Long
415 Unsupported Media Type
500 Internal Server Error
501 Not Implemented
502 Bad Gateway
505 Protocol Version Not Supported
Deleting all words in table "dict" for current URL
next_index_time=Now()+Period
Done
503 Service Unavailable
504 Gateway Timeout
next_index_time=Now()+Period
Done