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Q128325: XADM: Reclaiming Disk Space for the Information Store

Article: Q128325
Product(s): Microsoft Exchange
Version(s): winnt:4.0
Operating System(s): 
Keyword(s): kbenv
Last Modified: 04-AUG-2000

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The information in this article applies to:

- Microsoft Exchange Server, version 4.0 
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SUMMARY
=======

If the Information Store does not start due to lack of disk space, an
application event is logged in the Windows NT Event Viewer. The source is EDB
and the error test includes the Jet Blue error ID -1808. This article describes
how to free up disk space so that the Information Store can restart, and how to
use Windows NT Performance Monitor to track disk space usage in the future.

MORE INFORMATION
================

Monitoring Disk Space
---------------------

An Administrator can observe disk space usage on the drive containing the
Information Store by using the Windows NT Performance Monitor. The LogicalDisk
object along with the "% Free Space" and "Free Megabytes" counters are used to
monitor and trigger alerts when disk space is low.

Recovering Space Used by Log Files
----------------------------------

Increasing log files can cause the Information Store or Directory Store to run
out of operating space. To prevent this, do one of the following:

- Write the log files to a different drive.

- To change the location where the Information Store or Directory Store
  Transaction logs are written, select the Server object properties page and
  choose the Database Paths tab. Change the path for the Information Store and
  Directory Store transaction logs and click OK.

- Backup the Exchange Server.

- Use the Windows NT Backup utility that ships with Exchange Server to perform
  either a Normal (full) or Incremental Online backup of the server. The Backup
  utility automatically deletes transaction logs that are no longer needed
  (they have been committed to disk). If you never run the Backup utility, log
  files continue to grow.

- Correctly delete log files periodically.

- When the Information and Directory stores run, you find log files of the
  EDB*.LOG form in both the EXCHSRVR\DSADATA and EXCHSRVR\MDBDATA directories.
  Microsoft Exchange uses these log files to commit data to disk. In addition,
  these log files are necessary to perform Incremental and Differential type
  backup using the Windows NT Backup utility.

- The EDB*.LOG files can be deleted after the Directory and Information Store
  services have been shut down. If the log files are deleted when the services
  are still running, you can jeopardize data integrity. When the services are
  stopped, the transactions in these log files are committed to the main
  database file on disk (DIR.EDB for the directory and PRIV.EDB and PUB.EDB for
  the Information Store). When this data is committed, the log files are no
  longer needed. Follow the steps below to correctly delete log files:

  1. In Control Panel Services, select the Microsoft System Attendant Service
     and click STOP. This stops all Microsoft Exchange Services.

  2. Make a backup copy of the EDB*.LOG files in both the EXCHSRVR\DSADATA and
     the EXCHSRVR\MDBDATA directories. Copy them to an alternate location on
     the hard drive or to the tape backup.

  3. Delete all the EDB*.LOG files in both the EXCHSRVR\DSADATA and
     EXCHSRVR\MDBDATA directories.

  4. Restart all the Microsoft Exchange Server Services (in particular, the
     Directory and Information Store services).

  5. If these services do not start, restore the DSADATA and MDBDATA
     sub-directories from tape or hard disk. Restart the services again.

  6. If the services start, delete the backup copy of the DSADATA and MDBDATA
     sub-directories.

NOTE: If you delete the EDB*.LOG files in the manner described above, Incremental
and Differential backups of the Exchange Directory Store and Information Store
are no longer valid or possible. You can only perform a Normal type (full)
backup.

Circular Logging (which is enabled, by default - Advanced tab of the server
object's property page) writes log files, but once the checkpoint has been
advanced, the inactive portion of the transaction logs are discarded. Typically,
this represents the majority of the potential log data. The total size of the
active transactions are less than the total amount of RAM on a given computer.
Therefore, with circular logging enabled, the system has complete
recoverability, with respect to hard and soft crashes. The element that is
sacrificed is the protection against media failure. These methods are not
supported on servers, where Circular logging is enabled, because the transaction
logs are used for incremental and differential backups. An error message in
Windows NT Backup appears.

Checking a Database for Consistency
-----------------------------------

A Microsoft Exchange Server database is considered consistent only after normal
shut down. At all other times, including during normal operation, a flag in the
database marks it as inconsistent. Thus, if the database service is terminated
abnormally, Exchange Server detects something wrong on the next startup.
Exchange then initiates "soft recovery" steps to back out or commit necessary
transactions to the database and to restore its integrity.

You can check a database for consistency with the following command:

  eseutil /mh <database path and name> | more

The State line in the screen output from this command will contain Consistent or
Inconsistent.

You should not move inconsistent databases. Log files need to be played into that
database to make it consistent. Because the path is encoded into the log files
header information for the database, replay will not occur if you move the
databases.

For additional information on how to resolve a full transaction log drive, click
the article number below to view the article in the Microsoft Knowledge Base:

  Q259751 XADM: How to Recover from a Full Transaction Log File Drive

Additional query words:

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Keywords          : kbenv 
Technology        : kbExchangeSearch kbExchange400 kbZNotKeyword2
Version           : winnt:4.0

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