Tuesday, February 8, 2011

Active Directory Database and Log Files

Extensible Storage Engine (ESE) is the active directory database, which manage all the active directory objects in active directory database. Any of the data modification affects database performance, database fragmentation and data integrity

The ESE uses transaction and log files to ensure the integrity of the active directory database. Active Directory includes the following files:
*    Ntds.dit is the Active Directory database which stores the entire active directory objects on the domain controller. The .dit extension refers to the directory information tree. The default location is the %systemroot%Ntds folder. Active Directory records each and every transaction log files that are associated with the Ntds.dit file

*     Edb*.log is the transaction log file. Each transaction file is 10 megabytes (MB). When Edb.log file is full, active directory renames it to Edbnnnnn.log, where nnnnn is an increasing number starts from 1.

*      Edb.chk is a checkpoint file which is use by database engine to track the data which is not yet written to    
       the active directory database file. The checkpoint file act as a pointer that maintains the status between   
       memory and database file on disk. It indicates the starting point in the log file from which the information 
       must be recovered if a failure occurs.
*       Res1.log and Res2.log: These are reserved transaction log files. The amount of disk space that is reserved 
       on a drive or folder for this log is 20 MB. This reserved disk space provides a sufficient space to shut down if 
       all the other disk space is being used.

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