The DHCP (Dynamic Host Configuration Protocol) database is stored in the dhcp.mdb file, and it is located in \%systemroot%\system32\dhcp.
This database is prepared using Microsoft JET database technology, the same technology used for Microsoft Exchange Server, Active Directory, and many other databases in the Microsoft world.
As an administrator who has worked with JET databases will show, frequent maintenance of the DHCP database is needed to keep it functioning properly and to prepare it for defragmentation and recovery of whitespace.
By default, DHCP is configured to do online maintenance to the database, but only during intervals in which it is not being used for client requests.
For busy, large DHCP servers, there might never be downtime, so it is, therefore, significant to run offline maintenance against the dhcp.mdb file on a quarterly to semi-annual basis.
You can run maintenance against the dhcp.mdb DHCP database file by using the jetpack utility in Windows Server 2008. From the command line, enter the following commands to stop the DHCP Server service, compact the database, and start the service again:
1. cd %systemroot%\system32\dhcp
2. net stop dhcpserver
3. jetpack dhcp.mdb tmp.mdb
4. net start dhcpserver
NOTE: A maintenance schedule for DHCP and all other Microsoft JET-based databases should be established, in addition to any other maintenance schedules that might be in effect. Such a schedule will assist to keep these network services environments in top shape. Using redundant servers that will take over while the database is down can also minimize downtime from this maintenance.