HR / BAPI

hi guru's ,

i m using BAPI 'bapi_absence_create' for updating daily leave detail , but its giving error ' Employee/applicant is not locked yet' in program as well as in BAPI when executing in se37. can anybody tell me about this error and how can i remove it and also what is the function of lock indicator in this BAPI ?

suitable ans will be rewarded .

regards nitin.