ArcGIS applies and releases locks on datasets in a geodatabase as people edit and query data. These locks are needed to maintain the consistency of the data and versions, but they affect access to the locked objects.
From the Geodatabase Administration dialog box accessed from the database connection in ArcMap, you can view active locks on datasets and versions, which user has acquired each lock, and identify who may be blocking you from editing operations on specific datasets and versions. This helps you coordinate editing processes with others.
You can view the locks that apply to the data you own. Or, if you are the geodatabase administrator, you can view all data and version locks in the geodatabase. This lets the administrator see which connections may be blocking the completion of a maintenance task, such as reconciling data, compressing the geodatabase, or upgrading. The geodatabase administrator can use the list of locks to judge whether it is safe to remove the connections to allow those processes to run.
A geodatabase lock is always in one of two different modes: shared or exclusive.
ArcGIS automatically acquires a shared lock on an individual dataset when it is in use, for example, anytime a user is editing or querying the contents of a feature class or table. This mechanism is used so other users cannot make changes to the underlying dataset and its schema while it is in use. Any number of shared locks can be established on a single feature class or table at any given time.
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 reconcile a version. Once a user with proper permissions starts to make changes to a dataset in the geodatabase, ArcGIS automatically establishes an exclusive lock on the individual attribute table, feature class table, raster table, or other dataset. However, if a shared lock exists on that dataset, an exclusive lock cannot be established.
An exclusive lock is promoted from a shared lock and demoted back to a shared lock when no longer needed. Only one exclusive lock is allowed at a time on a dataset or version.
There are three different types of locks in an enterprise geodatabase: schema locks, state locks, and version locks.
A shared schema lock is acquired anytime a dataset is opened in ArcGIS. When the schema of the dataset is modified in any way, that shared schema lock is promoted from shared to exclusive for the duration of the schema changes. This provides consistency in a multiuser environment by preventing the schema of a dataset from changing when other users have that dataset open.
Data owners can view schema locks held on their data. Geodatabase administrators can see all schema locks in the geodatabase.
A shared state lock is acquired anytime a traditional version representation of a dataset is open in ArcGIS.
Only geodatabase administrators can view state locks.
A shared version lock is acquired when an edit session is started for a given traditional version. When a traditional version is reconciled with a target version, the shared version lock is promoted to an exclusive lock for the duration of the reconcile operation. If two users are editing the same version, both hold a shared lock on that version. Neither user can reconcile with a target version, which requires an exclusive lock, until the other user stops editing, thereby releasing his shared lock on the version.
Only geodatabase administrators can view version locks.