Schema Lock: Add Field vs. Editing

[deleted-user-VeC5jUIlNXtq]

Hey all,

I thought I understood this concept better than I do, but apparently not. I need a refresher course.

I understand the basics of schema locks, however I'm having trouble with something simple.

I've got a couple feature classes in a file geodatabase (ArcGIS for Desktop Basic 10.1, simple feature classes, nothing complex).

My colleague has several mxd's open which have these feature classes as layers. I'd appreciate it if someone could provide me a detailed explanation of why I'm able to edit these datasets (add/delete data, etc...), but unable to Add a field to the attribute table. I didn't get the explanation I was looking for from the help files.

I was under the impression that schema locks for read access and locks for editing were different. I guess I thought that, if someone is editing that feature class, it's locked fully, but if they're simply accessing it, I could perform things like Add field or edit.

Long story short: what are the specific differences of "Add Field" and Editing a feature class in terms of locks. A less important, but if you have time question: do shapefiles share the same type of locks?

I hope that makes sense, and thanks for your time!

[NidhinKarthikeyan]

Its not possible to make edits(at the same time) on the multiple feature class residing in same Feature dataset(File Geodatabase/Personal Geodatabase/Shape file). One can just view the feature class drawn on ArcMap. A field cannot be added on feature class if the
feature class is opened in another ArcMap session/mxd.

Shape file share the same type of lock.

Exception is Versioned editing in ArcSDE.

[deleted-user-VeC5jUIlNXtq]

Yes I'm aware that editing is locked for multiple instances (only 1 person editing at a time), however that's not the case.

I'm curious why I'm able to edit, when the feature class is already open (being read), but I can't add a field. I'd like to know the specifics of the details of the lock.

I know what happens with locks, I'm looking for why it happens.

[NidhinKarthikeyan]

You can open a Tech Support Incident. Any of the Analyst or someone from Development Team will be able to answer it.

[deleted-user-VeC5jUIlNXtq]

I don't believe this is a bug though. I'm not questioning whether or not it should be happening, I'm looking for the reason why it's happening.

Why am I not able to add a field (what I consider to be a relatively minor edit), but able to edit the actual features (something I consider to be relatively major edit). I'm not clear on the specifics.

[AsrujitSengupta · Accepted solution]

Geoff,

What you are experiencing, is the expected behaviour of the software. This is something by design.

Locks are of various kinds....Shared Locks, Exclusive Locks...

While editing or viewing data, a Shared Lock is established.... Any number of shared locks can be established on a single feature class or table at any given time. When you use ArcGIS to modify your geodatabase schema???for example, to add a field or alter rules???ArcGIS attempts to establish an exclusive lock on the data being altered. However, if a shared lock exists on that dataset, an exclusive lock cannot be established.

An exclusive lock is used to lock a dataset in the geodatabase from use by others to make necessary changes to it; for example, to alter the dataset's schema. Once a user with proper permissions starts to make changes to a dataset in the geodatabase, ArcGIS will automatically establish an exclusive lock on the individual attribute table, feature class table, raster table, or other dataset.
If a user wants to make changes to a geodatabase schema, the specific datasets with which he or she is working must not be in use by others. In other words, to make changes to a dataset, a shared lock must not exist on that dataset.

Mentioned in detail in the below link:
Schema locking:
http://resources.arcgis.com/en/help/main/10.1/index.html#//003n0000002m000000

FAQ: How are the various lock mechanisms implemented in ArcSDE and the geodatabase?
http://support.esri.com/en/knowledgebase/techarticles/detail/27034


Hope this helps!

[deleted-user-VeC5jUIlNXtq]

Great, that is a big help.

Thanks very much!