Can anyone help me out with this error. While importing employee data in contract from data exceeded error occurs. 

Note : We have already imported 70000 employee data in our database. We also tried importing 100 data per file still the below error occurs.

Error:

"An unknown issue occurred during import (possibly lost connection, data limit exceeded or memory limits exceeded). Please retry in case the issue is transient. If the issue still occurs, try to split the file rather than import it at once"