The global constants for locks are listed in the following table.
| Global Constant | Integer Value | Description |
|---|---|---|
| Exclusive_Lock | 3 | No other process can lock the same object. |
| Get_Lock | 0 | Not valid for lock requests. This lock type indicates a process is waiting to acquire a lock that will cause all other lock requests for the object to be queued (for example, when upgrading a lock from update to exclusive). |
| Reserve_Lock | 2 | When you place a reserve lock on an object, other processes attempting to acquire an exclusive lock or reserve lock on that same object wait until the reserve lock is relinquished, but those attempting to acquire a shared lock succeed. |
| Share_Lock | 1 | When you place a shared lock on an object, other processes attempting to update the object or explicitly acquire an exclusive lock wait until the lock is released but can acquire a shared lock or a reserve lock. |
| Update_Lock | 4 | Placing an update lock allows you to update the object, while still allowing other processes to acquire shared locks to view the most recently committed edition. |