Is there any coding? Where it can written? What is it? Mention coding?

in pa30 system is not letting me to create personnel no .it is giving error like no entries were found in table T503,i was generated numeric feature ,defined number ranges ,integrated om &pa .i checked in table entries were there but system is not letting me to create personnel no .please any one rectify this problem .

Since BDC is interface between SAP and Non-SAP, is it possible? Explain with example

I need to write some code after save at user command