DHCP servers store DHCP lease and reservation information in database files. By default, these files are stored in the %SystemRoot%\System32\DHCP directory. The key files in this directory are used as follows:
Dhcp.mdb The primary database file for the DHCP server
J50.log A transaction log file used to recover incomplete transactions in case of a server malfunction
J50.chk A checkpoint file used in truncating the transaction log for the DHCP server
Res1.log A reserved log file for the DHCP server
Res2.log A reserved log file for the DHCP server
Tmp.edb A temporary working file for the DHCP server
The backup directory in the %SystemRoot%\System32\DHCP folder contains backup information ...