Any map service (Including ArcIMS and Dekho map services), that connects to ArcSDE feature classes, places a schema lock on the dataset that is participating in the associated map service.
A schema lock occurs when another application is accessing the database object (featureclass/table), and you are attempting to alter its structure by, for example:
a) adding or removing a field or;
b) adding or removing a feature class / table
If the Feature class resides in a Feature Dataset, there will also be a lock on *all* the other Feature classes in the Feature dataset.
Also, if your data is Versioned and you are editing and compressing your SDE data on a regular basis, it is important, that their are no applications accessing the data when running the SDE compress command or tool. If there are, the edits will not move to the Business / base table due to the locking application.
To disable the map service schema lock, you can set the tag to false. This tag can be added to the services configuration file (.cfg) for the map service found in
C:\Program Files (x86)\ArcGIS\Server10.0\server\user\cfg
More information on this tag can be found via the ArcGIS Server web help:
To set this parameter you need to do the following:
1. Stop the SOM service
2. Open the .cfg file for the map service located in C:\Program Files\ArcGIS\Server 10.0\server\user\cfg (or alternatively
C:\Program Files\ArcGIS\server\user\cfg )
3. Edit the file by adding the following line false
to the Properties tag as follows:
4. Save and close .cfg file
5. Restart SOM service
6. You can make a schema change while the map service is running.
This tag is really useful for clients whose data is registered as versioned and compress their data regularly or are performing schema changes on a nightly basis through ArcGIS geoprocessing tools via Python or some other ArcGIS Process.