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7.2 LockingServices Type ToC Previous Next index

The LockingServicesType provides Methods to manage the lock and Properties with status information. This section describes the common semantic. The lock-owner ObjectTypes will often extend these semantics.

Figure 31 shows the LockingServicesType definition. It is formally defined in Table 54.

readme_files/image033.png Figure 31 – LockingServicesType

Table 54 – LockingServicesType definition

Attribute Value
BrowseName LockingServicesType
IsAbstract False

Subtype of the BaseObjectType defined in OPC 10000-5.

References NodeClass BrowseName DataType TypeDefinition ModellingRule
HasComponent Method InitLock Defined in 7.5 Mandatory  
HasComponent Method RenewLock Defined in 7.7 Mandatory  
HasComponent Method ExitLock Defined in 7.6 Mandatory  
HasComponent Method BreakLock Defined in 7.8 Mandatory  
HasProperty Variable 0:DefaultInstanceBrowseName QualifiedName PropertyType  
HasProperty Variable Locked Boolean PropertyType Mandatory
HasProperty Variable LockingClient String PropertyType Mandatory
HasProperty Variable LockingUser String PropertyType Mandatory
HasProperty Variable RemainingLockTime Duration PropertyType Mandatory
Conformance Units          
DI Locking          

The StatusCode Bad_MethodInvalid shall be returned from the Call Service for Objects where locking is not supported. Bad_UserAccessDenied shall be returned if the Client User does not have the permission to call the Methods.

The DefaultInstanceBrowseName Property – defined in OPC 10000-3 – is used to specify the recommended BrowseName for instances of the LockingServicesType. Its Value is defined in Table 55.

Table 55 – LockingServicesType Additional Variable Attributes

Source Path Value
0:DefaultInstanceBrowseName Lock

A lock is typically initiated by a Client calling the InitLock Method and removed by calling the ExitLock Method. The lock-owner ObjectTypes can define mechanisms that automatically initiate and remove a lock.

A lock request will be rejected if operations are active that will be prevented by the lock.

The lock is automatically removed if the MaxInactiveLockTime has elapsed (see 7.4). The lock is also removed when the Session ends during inactivity. This is typically the case when the connection to the Client breaks and the Session times out.

The following LockingServices Properties offer lock-status information.

Locked when True indicates that this element has been locked by some Application and that no or just limited access is available for other Applications.

When the lock is initiated by a Client, LockingClient contains the ApplicationUri of the Client as provided in the CreateSession Service call (see OPC 10000-4). Other options to get this information can be specified on the lock-owner ObjectType.

LockingUser contains information to identify the user. When the lock is initiated by a Client it is obtained directly or indirectly from the UserIdentityToken passed by the Client in the ActivateSession Service call (see OPC 10000-4). Other options to get this information can be specified on the lock-owner ObjectType.

RemainingLockTime denotes the remaining time in milliseconds after which the lock will automatically be removed by the Server. This time is based upon MaxInactiveLockTime (see 7.4).

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