RE: When Posting on General Journal, rows dissapears
Check how the process flow works and you will understand the logic. In NAV assume posting means you completed the transaction, so it will delete the transaction from that table and transfer those posted tables, in this case it will transfer the entry to GL Entry and based on Account Type and other fields it will create additional records in other Ledger Entry tables.
Journal Line tables: Gen. Journal Line , Item Journal Line.
Related Posted Tables: G/L Entry, Item Ledger Entry, Cust. Ledger Entry........