OPCClient Object

OPC Data Access Server Security Settings

In order for the OPCClient object to connect to a third-party OPC DA Server, certain security settings are required on the third-party OPC DA Server node.

Note These same settings must be applied to OPCEnum if the OPCClient is to use the server name instead of the progID.

If the OPC Server is a Wonderware DAServer, no additional configuration is required.

The recommended settings are explained as follows. All of these setting can be set with Windows utility DCOMCnfg.Exe.

Run DCOMCnfg.Exe.

In the list of applications, select the OPC DA Server and then click Properties.

Note Under some conditions, the third-party OPC DA Server may not appear in the list of applications. In this case, you will need to create server specific AppID and run DCOMCnfg.Exe again. For information on creating AppID for COM objects, see the Microsoft documentation.

Click the General tab.

In the Authentication Level list, click None. (The default setting is "Default.")

The authentication level informs the component object model (COM) how much authentication protection is required, and it can range from authenticating the client at the first method call to encrypting parameter states fully.

Click the Security tab to configure who is allowed to launch permissions and access permissions to the server.

The launch permissions control the list of users who are granted or denied permission to launch a particular server.

You can control the list of users who are granted or denied access to the methods of a particular server by setting access permissions. You can add users or groups to the list, specifying whether access permission is being granted or denied. You can also remove users from the list.

When setting access permissions, you must ensure that both SYSTEM and Everyone are included in the list of users that are granted access.

Select Use custom access permissions and Use custom launch permissions.

For each of them, click Edit and then add "Everyone" and "System" to the list of users allowed to access and launch the server.

Click the Identity tab to configure the identity of the server.

An application's identity is the account that is used to run the application. The identity can be that of the user that is currently logged on (the interactive user), the user account of the client process that launched the server, a specified user, or a service. Thus, you can select from one of the following three options:

The interactive user
The interactive user is the user that is currently logged on to the computer where the application is running. If the identity is set to be the interactive user, all clients use the same instance of the server if the server registers its class factory as multi-use. If no user is logged on, the application will not run. If the server has a graphical user interface (GUI) that the client needs to see, you should use interactive user for the application's identity. However, choosing this identity carries some security risks because the server runs under the identity of the logged on user without the logged on user's knowledge or consent.

The launching user
This is the default setting for the application identity. When the launching user is chosen for the application's identity, each client account gets a new instance of the server, and each server gets its own WinStation. Because of the separate server instances, launching user is the most secure identity setting. However, there are limits on resource consumption. Also, any GUI the server displays will not be seen by the client. Although this is the option selected by default, we recommend to avoid selecting this option.

This user
Specifying a particular user (and the user's password) is the preferred identity for COM servers. The reason this identity is preferred is that no one has to be logged on the machine where the server is running for the server to run, and every client talks to the same instance of the server if the server registers its class factory as multi-use. If the server has GUI, then you should not choose this identity; if you do, the user will not be able to see the user interface. Running as a fixed user account is more secure than the interactive user identity because this identity can only be assigned to the application by someone who has the specific user's password.

Related Topics

Scan Groups

A scan group, or device group, is a collection of attributes that have a common update interval. When you configure the OPCClient object, you will need to specify at least one scan group in order to deploy the object. Within each scan group, you can specify data items to use as the object attributes. At run time, items for a scan group will be updated with the latest values from the OPC DA Server according to the update interval.

From other objects and from scripts, you can reference the attributes (items) you configured for the OPCClient object. For example, you might configure the input source for a FieldReference object to reference an item for one of the scan groups. Thus, the FieldReference object input source would be receiving data from an OPC DA Server via the OPCClient object.

Tip You can use any OPC client tool to browse a field device's address space for item names.

The reference syntax for a OPCClient object data point is:

<objectname>.<scangroupname>.<itemname>

The <objectname> is the name that you choose to give to the OPCClient object.

The value of <itemname> depends on the type of OPC DA Server you are connecting to. For information on how to reference data points in the OPC DA Server, see the server documentation.

Run-time object attributes allow you to monitor errors related to the data quality for item values in a scan group.

Related Topics

Block Reads and Block Writes

A block read is a set of attributes that can be used to retrieve values in a single transaction. Instead of the I/O points being on advise, as with a scan group, the attributes are updated once per transaction. A block read must be initiated from a user or script via the BlockRead.TransactionTrigger attribute.

A block write is a set of attributes that can be used to write values in a single transaction. Only values that are new for the attribute since the last transaction are written to the OPC DA Server. A block write must be initiated from a user or script via the BlockWrite.TransactionTrigger attribute. You cannot trigger another transaction if the previous transaction has not completed.

Note Although block reads and writes are intended to be individual transactions, the actual communication with the field device is dependent on the number and type of attributes, and it may be necessary to send and receive multiple messages to and from the field device. As a result, the values exposed after a block read operation might have been obtained at different times. You must carefully design the logic in the field device to make sure that the values do not change until the full read operation is completed. In the case of a block write operation, the logic in the field device must not use the written values until the full write operation is completed.

For a block read, either all of the attributes will be updated or none of the attributes will be updated; no partial updates are supported. In the case of a block read failure or transaction timeout, the data quality for all attributes is set to BAD.

For a block write, partial writes are supported. However, the system does not offer roll-back functionality. In the case of a block write failure or transaction timeout, some values may have been successfully sent, but there is no way to undo the value changes. For items that have not yet been written to, the data quality is set to BAD.

Finally, run-time object attributes allow you to monitor errors related to the data quality for item values in a block read or block write operation.

Related Topics

Scan Groups

Run-Time Behavior

The following information describes the run-time behavior of OPCClient objects. Run-time behavior is limited to the state of individual OPCClient objects.

After it has been deployed and is operating, an OPCClient object can assume one of several states, which are described in the following table:


State Change	Behavior
Startup	In this state, the OPCClient object connects to the OPC DA Server.
Going onscan	None.
Running onscan	In this state, the OPCClient object: Services read and write requests. Receives values from the OPC DA Server scan groups (device groups). Monitors the connection to the OPC DA Server. Detects alarm conditions, if alarming is enabled. Monitors the data quality for OPC DA Server data values and updates run-time error statistics if the quality is not GOOD.
Going offscan	None. The ConnectionStatus attribute is set to "Disconnected."
Offscan	The object is passive and does not service read and write requests.
Shutdown	In this state, the OPCClient object disconnects from the OPC DA Server.

Related Topics

Configuration

The following table describes the object editor options for configuration and the associated attributes:


Topic Category	Topic Subcategory	Topic Details
Configuration	General Configuration
	Scan Group Configuration
	Block Read Configuration
	Block Write Configuration
	Using the OPC Item Browser
	Example Configuration

For general information on objects, including relationships, deployment, and alarm distribution, see the Integrated Development Environment (IDE) documentation.

For information on configuration options of object scripts, attributes, or features, click Attributes Help in the Help file header.

Related Topics

General Configuration

Use the General tab to specify the OPC DA Server from which to retrieve data and to configure restart options.


Editor Option	Associated Attribute	Description	Run-Time Access (Supervisory, User, Read-Only, None)
Server node	ServerNode	The name of the node (computer) on which the OPC DA Server is running. If this attribute is blank, the OPC DA Server is assumed to be running on the local node. Click the Browse button to find the network for the node.	Supervisory, User
Server name	ServerName	The name of the OPC DA Server. The naming syntax for the OPC DA Server varies according to the type.	Supervisory, User
Run server out-of-proc	ServerActivation	If enabled, the OPC DA Server will be run out-of-process. An in-process OPC DA Server runs as a .Dll within the engine process. An out-of-process OPC DA Server runs as a stand-alone executable. The method you choose depends on the methods supported by the OPC DA Server and performance considerations. To connect to the OPC DA Server in-process, all of the following must be true: The OPC DA Server must be installed locally relative to where the OPCClient is installed. The OPC DA Server must support an in-process connection. The OPC DA Server is not currently running out-of-process. The value of the ServerNode attribute must be blank. This Run server out-of-proc check box must be unchecked.	Read-Only
Use scan group name as access path	DAGroupAsAccessPath	If enabled, the name of the scan group will be used for the OPC access path. Select this option for OPC DA Servers that require a topic to be specified for the access path. You must then make sure that any scan group you specify is named the same as a topic within the OPC DA Server.	Read-Only
Restart attempts	RestartMax	The maximum number of times that the OPCClient object should attempt to restart a failed OPC DA Server within the restart period.	Supervisory, User
Restart period	RestartPeriod	The time period, in milliseconds, over which the maximum number of restart attempts applies. If this time period elapses before the maximum number of restarts is exceeded, then the restart count is set back to zero.	Supervisory, User
Detect restart alarm	RestartAlarm.Alarmed	If enabled, an alarm will be triggered when the number of attempts to start the OPC Server has exceeded the allowed maximum within the restart period.	None
Priority	RestartAlarm.Priority	See Alarm Attributes.	Supervisory, User
Connection heartbeat period	ConnectionHeartbeatPeriod	The time interval, in milliseconds, at which the OPCClient object will check the connection to the OPC DA Server.	Supervisory, User
Detect connection alarm	ConnectionAlarm.Alarmed	If enabled, an alarm will be triggered when the OPCClient object can no longer communicate with the OPC Server.	None
Priority	ConnectionAlarm.Priority	See Alarm Attributes.	Supervisory, User
Restart reset security	RestartReset	Used to set security for restarting the OPC DA Server.	Supervisory, User

Related Topics

Scan Group Configuration

Use the Scan Group tab to add scan groups to the OPCClient object.


Editor Option	Associated Attribute	Description	Run-Time Access (Supervisory, User, Read-Only, None)
Scan Group	ScanGroupList	A unique name for a scan group (device group) in the OPC DA Server from which you want to receive data. Use the Add (plus sign) button to add a group to the list. Type the group name. To delete a group, select the topic in the list and click the Delete (cross sign) button.	Read-Only
Update Interval	ScanGroup.UpdateRateCmd	The rate, in milliseconds, at which the object will receive updated data values for the scan group. The default is 250.	Supervisory, User
Scan Mode	ScanMode	The scanning mode for the scan group, either ActiveOnDemand, Active, or ActiveAll. For the ActiveOnDemand mode, attributes that are not actively being referenced by any client or object are not scanned. For the Active mode, an attribute is always in the active scanning state. When the last reference to the attribute is unregistered (unadvised) , the attribute is deleted. For ActiveAll, an attribute is always in the active scanning state, but when the last reference to the attribute is unregistered (unadvised), the attribute is not deleted.	Supervisory, User
Attribute	ScanGroup.ItemList	A user-defined name for an item reference. This name is also known as the alias. The maximum number of attributes that can be preconfigured is 5000.	None
Item Reference	ScanGroup._AliasReference	The item address in the OPC DA Server.	None
import button	<scan group name>.ItemList	Click to import item data from a .csv file for the selected scan group. A dialog box will appear in which you can specify the file to import. The imported .csv data will be inserted as the associated attributes for the selected scan group. Each attribute and its item reference will be added to the list, as long as there is not already a configured reference with the same attribute name. For duplicate references, you will be prompted to replace the existing reference with the new reference, or ignore the new reference. The import button is unavailable if no scan group is selected or if the associated attributes section is locked from the parent object.	None
export button	<scan group name>.ItemList	Click to export item data to a .csv file. A dialog box will appear in which you can specify the name and location of the file to be exported. The resulting .csv file will contain one row for each attribute item. Each row includes two columns: Attribute Name and Item Reference. You can edit the file using Microsoft Excel or a text editor. The export button is unavailable if no scan group is selected or if there is no existing associated attribute.	None

To use the OPC Item Browser to configure attributes for each scan group, click the ellipses button that appears at the far right of the Associated attributes list when you click the Add button (plus sign). For more information about the OPC Item Browser, see Using the OPC Item Browser.

Related Topics

Block Read Configuration

Use the Block Read tab to configure a set of items for which values will be read from the OPC DA Server in a single transaction.


Editor Option	Associated Attribute	Description	Run-Time Access (Supervisory, User, Read-Only, None)
Block Read	BlockReadList	A unique name for a block read group. Use the Add (plus sign) button to add a group to the list. You will need to type in the group name. To delete a group, select the topic in the list and click the Delete (cross sign) button.	Read-Only
Transaction Timeout	BlockRead.TransactionTimeout	The amount of time, in milliseconds, allowed for the block read transaction to complete. The default value is 0. There is no transaction timeout when this value is 0.	Read-Only
Access Path	BlockRead.AccessPath	The OPC address path. The path syntax is specific to the type of OPC Server.	Read-Only
Attribute	BlockRead.ItemList	A user-defined name for an item reference. This name is also known as the alias. The maximum number of attributes that can be preconfigured is 5000.	None
Item Reference	BlockRead._AliasReference	The item address in the OPC DA Server.	None
import button	<block read name>.ItemList	Click to import item data from a .csv file for the selected block read name. A dialog box will appear in which you can specify the file to import. The imported .csv data will be inserted as the associated attributes for the selected block read name. Each attribute and its item reference will be added to the list, as long as there is not already a configured reference with the same attribute name. For duplicate references, you will be prompted to replace the existing reference with the new reference, or ignore the new reference. The import button is unavailable if no block read name is selected or if the associated attributes section is locked from the parent object.	None
export button	<block read name>.ItemList	Click to export item data to a .csv file. A dialog box will appear in which you can specify the name and location of the file to be exported. The resulting .csv file will contain one row for each attribute item. Each row includes two columns: Attribute Name and Item Reference. You can edit the file using Microsoft Excel or a text editor. The export button is unavailable if no block read name is selected or if there is no existing associated attribute.	None

To use the OPC Item Browser to configure attributes for each block read group, click the ellipses button that appears at the far right of the Associated attributes list when you click the Add button (plus sign). For more information about the OPC Item Browser, see Using the OPC Item Browser.

Related Topics

Block Write Configuration

Use the Block Write tab to configure a set of items for which values will be written to the OPC DA Server in a single transaction.


Editor Option	Associated Attribute	Description	Run-Time Access (Supervisory, User, Read-Only, None)
Block Write	BlockWriteList	A unique name for a block write group. Use the Add (plus sign) button to add a group to the list. You will need to type in the group name. To delete a group, select the topic in the list and click the Delete (cross sign) button.	Read-Only
Transaction Timeout	BlockWrite.TransactionTimeout	The amount of time, in milliseconds, allowed for the block read transaction to complete. The default value is 0. There is no transaction timeout when this value is 0.	Read-Only
Access Path	BlockWrite.AccessPath	The OPC address path. The path syntax is specific to the type of OPC Server.	Read-Only
Attribute	BlockWrite.ItemList	A user-defined name for an item reference. This name is also known as the alias. The maximum number of attributes that can be preconfigured is 5000.	None
Item Reference	BlockWrite._AliasReference	The item address in the OPC DA Server.	None
import button	<block write name>.ItemList	Click to import item data from a .csv file for the selected block write name. A dialog box will appear in which you can specify the file to import. The imported .csv data will be inserted as the associated attributes for the selected block write name. Each attribute and its item reference will be added to the list, as long as there is not already a configured reference with the same attribute name. For duplicate references, you will be prompted to replace the existing reference with the new reference, or ignore the new reference. The import button is unavailable if no block write name is selected or if the associated attributes section is locked from the parent object.	None
export button	<block write name>.ItemList	Click to export item data to a .csv file. A dialog box will appear in which you can specify the name and location of the file to be exported. The resulting .csv file will contain one row for each attribute item. Each row includes two columns: Attribute Name and Item Reference. You can edit the file using Microsoft Excel or a text editor. The export button is unavailable if no block write name is selected or if there is no existing associated attribute.	None

To use the OPC Item Browser to configure attributes for each block write group, click the ellipses button that appears at the far right of the Associated attributes list when you click the Add button (plus sign). For more information about the OPC Item Browser, see Using the OPC Item Browser.

Related Topics

Using the OPC Item Browser

The OPC Item Browser allows you to browse the namespace of an OPC Server and choose items to add to a scan group, block read group, or block write group.

The browser has seven main components:

Branches window – displays the logical groupings of items as configured in the application.

Available Items window – displays all items associated with the grouping selected in the Branches window.

Basket (Selected Items) window – displays those items that have been selected from the Available Items list for inclusion in a scan group, block read or block write group. To add items to the Basket, select one or more in the Available Items window (multi-select is allowed) and click Add (the plus sign). Alternatively, you can click-and-drag items to the Basket; select items and press Enter; or right-click the selected item(s) and click Add to Basket on the options menu. Duplicate items will not be added to the basket.

OK button – closes the browser and adds items in the Basket window to the Associated attributes list in the object’s editor.

Filter button – starts the Specify Filter Criteria dialog box, in which you can set filtering criteria that restricts the data shown in the Available Items window. See "Specify Filter Criteria Dialog Box" below for more information.

Cancel button – closes the browser and does not add items in the Basket window to the Associated attributes list in the object’s editor.

Status bar – based on the cursor location, it displays hint information such as which application you are browsing and the node it is located on, or what to do when items are selected in the Available Items window.

Note When you click OK, each item in the Basket window becomes a separate attribute in the object editor’s Associated attributes list. If a Basket item already exists in the Associated attributes list, it is not added again to the list and a message is displayed informing you that some item(s) in the Basket list were duplicates.

Note When you close the browser with either the OK or Cancel button, the Basket window and all filter criteria is reset.

Properties Dialog Box

Use the properties dialog box to view application data about an item selected in the OPC Item Browser. This dialog box is for information only; you cannot change the data shown.

Open the dialog box by right-clicking on an item and clicking Properties in the option menu. Click the close button (X) to close the dialog box.

The title bar displays the application grouping hierarchy (as shown in the Branches window of the browser) and the item selected. Two columns of data display each property and its current value.

Specify Filter Criteria Dialog Box

Use the Specify Filter Criteria dialog box to control the number of items displayed in the Available Items window of the browser. After you set filter criteria, it applies to the items shown for any group selected in the Branches window of the browser.

Click the Filter button on the browser to open this dialog box. Click OK to close it and activate the filter criteria; click Cancel to close with no filter criteria set.

Note Filter criteria stays in effect on displayed browser contents until the browser is closed. At that point, the filter dialog box displays the default settings, as shown below.

The filter dialog box provides three sets of filters:

Item Name – type a specific item’s name or use wildcards (* and ?) to widen the range. Default setting is all item names (*). Wildcards function like typical Windows wildcards: * replaces several characters, ? replaces a single character.

Item Data Type – select "Any" or one of the following OPC data types: short, integer, float, real, currency, data, string, boolean or unsigned char. If the data type is an array element, click the checkbox. The item syntax for array elements is <sg>.Attribute(<item>)[<index>]. Default settings are "Any" and unchecked.

Item Access Rights – select the type of OPC access rights of the desired items: Readable Only, Writeable Only or Readable and Writable. Default setting is "Readable and Writable."

Related Topics

General Configuration

Example Configuration

The following is an example of how to configure an instance of $OPCClient to connect to the OPC Server associated with an instance of $ABTCPPLC5. This example is atypical because you do not need to use an $OPCClient instance to communicate with this OPC Server; the $ABTCPPLC5 instance already does that. Instead, the purpose of this example is to illustrate the correct namespace syntax to use when adding items to the OPCClient object.

For the example, assume the following:

An Allen-Bradley PLC5 is connected to the network.

Wonderware Application Server is installed.

The ABTCP.aPKG and ABTCPPLC5.aaPKG templates have been imported into the IDE.

Step 1: Configure the $ABTCPPLC5 Instance

Assume you have a WinPlatform called P01.

To configure the instance

Create following hierarchy of objects as seen from the deployment view:

Edit ABTCPPLC5_001.

Specify the host name (that is, the IP address of the PLC).

Tip From a command prompt, you should be able to execute a PING command to the IP address of the PLC and get a response.

Click the Scan Group tab and add a scan group. For example, SG1.

Save and close the editor.

Step 2: Deploy the $ABTCPPLC5 instance and test connectivity to the PLC

To deploy and test

In the IDE, deploy the four objects onscan by choosing to cascade deploy on P01.

Note In Windows Task Manager, you should see DASABTCP.exe. This is the DAServer, which is also an OPC Server.

In Object Viewer, right-click on ABTCPPLC5_001 and click View.

Check that the ABTCPPLC5_001.ConnectionStatus attribute indicates "Connected."

In Object Viewer, add ABTCPPLC5_001.SG1.s2:23 to the watch. In this example, s2:23 is the current second of the PLC time.

This item's value should change every second. If so, the ability to read data from the PLC has been confirmed.

Step 3: Configure the $OPCClient instance

To configure the instance

Create an OPCClient_001 instance from $OPCClient and assign it to AppEngine_001.

Edit OPCClient_001.

Specify the server node. For this example, assume SERVER1 is the node name.

Do the following:

In the Server name list, click ArchestrA.DASABTCP.1.

Click the Scan Group tab add a scan group. For this example, add SG2.

Click the + sign to add associated attributes for SG2:

Click the ellipsis (...) button that appears below the Item Reference column to browse the OPC Server. This launches the OPC item browser.

Expand the tree.

Click on ABTCPPLC5_001.

Right-click on $Sys$ItemCount and click Add to Basket.

Browsing helps you understand the namespace of the DASABTCP.exe OPC Server. Now that you know how to get registers from the PLC, the syntax will be:

OPCClient001.SG2.ABTCP_001.ABTCPPLC5_001.PlcRegisterName

Click OK.

Save and close the editor.

Step 4: Deploy the $OPCClient instance and test connectivity to the PLC

To deploy the instance and test connectivity

Deploy OPCClient_001.

In Object Viewer, check that the OPCClient_001.ConnectionStatus attribute indicates "Connected."

In Object Viewer, add the OPCClient_001.SG2.ABTCP_001.ABTCPPLC5_001.$SYS$ItemCount attribute to the watch window. After a couple of seconds, the attribute should indicate a value and a quality of C0:GOOD.

If you want to see register s2:23 as part of the OPCClient (as opposed to part of the ABTCPPLC5 object), add the OPCClient_001.SG2.ABTCP_001.ABTCPPLC5_001.s2:23 attribute to the watch window.

An additional way to understand the DAServer's namespace is by using the System Management Console (SMC). Open the SMC, and then click on DAServer Manager. For example:

Related Topics

General Configuration

Run-Time Object Attributes

The following table describes the run-time only attributes for the object.


Topic Category	Topic Subcategory	Topic Details
Run-Time Object Attributes	Alarm Aggregation Attributes
Run-Time Object Attributes	Alarm Attributes

Note Configurable run-time attributes are described in the configuration sections. For more information, see Configuration.

For a list of common attributes, click Attributes Help in the Help file header.


Attribute	Description	Run-Time Access (Supervisory, User, Read-Only, None)
AlarmDSCnt	The total number of disabled and silenced alarms in the object. Sub-areas or sub-notification-distributors are not included.	Read-Only
AlarmOnCnt	The number of active alarms in the distributor. Does not include sub-areas or sub-notification-distributors.	Read-Only
AlarmUnAckCnt	The number of unacknowledged alarms in the distributor (including unacknowledged return-to-normals). Does not include sub-areas or sub-notification-distributors.	Read-Only
BlockRead.AliasDatabase	Used to store pairs of alias attribute names and the corresponding item references.	Read-Only
BlockRead.ItemCnt	The total number of items in the group that are on advise by a client application.	Read-Only
BlockRead.ItemErrorCnt	The current number of items that have been successfully added to this group and have data quality other than GOOD. This value is calculated.	Read-Only
BlockRead.ItemErrorCntAlarm	Set to TRUE if the current error count is not zero. This value can be alarmed.	Read-Only
BlockRead.ItemErrorCntLast	The error count immediately prior to the current error count.	Read-Only
BlockRead.ItemErrorCntLastEnd	The last time the error count returned to zero. The date format reflects the current locale setting for the operating system.	Read-Only
BlockRead.ItemErrorCntLastStart	The last time that the error count changed from zero to non-zero, not including the most recent change to the error count. The date format reflects the current locale setting for the operating system.	Read-Only
BlockRead.ItemErrorCntStart	The time that the error count most recently changed from zero to non-zero. The date format reflects the current locale setting for the operating system.	Read-Only
BlockRead.StatsReset	Used to reset all statistics during run time.	Supervisory, User
BlockRead.TransactionComplete	Set to TRUE when the transaction has completed.	Read-Only
BlockRead.TransactionEnd	The time the last transaction ended. The date format reflects the current locale setting for the operating system.	Read-Only
BlockRead.TransactionsCnt	The total number of transactions since the last statistics reset.	Read-Only
BlockRead.TransactionStart	The time the last transaction started. The date format reflects the current locale setting for the operating system.	Read-Only
BlockRead.TransactionStatus	Used to indicate the status of the transaction. Valid values are: InActive, Processing, and Completed.	Read-Only
BlockRead.TransactionTimeAvg	The average amount of time required to process this group since the last statistics reset.	Read-Only
BlockRead.TransactionTimeMax	The longest amount of time required to process this group since the last statistics reset.	Read-Only
BlockRead.TransactionTimeMin	The shortest amount of time required to process this group since the last statistics reset.	Read-Only
BlockRead.TransactionTimeoutAlarm	Set to TRUE if the transaction timeout has been exceeded.	Read-Only
BlockRead.TransactionTrigger	If TRUE, the transaction will be started.	Supervisory, User
BlockWrite.AliasDatabase	Used to store pairs of alias attribute names and the corresponding item references.	Read-Only
BlockWrite.ItemCnt	The total number of items in the group that are on advise by a client application.	Read-Only
BlockWrite.ItemErrorCnt	The current number of items that have been successfully added to this group and have data quality other than GOOD. This value is calculated.	Read-Only
BlockWrite.ItemErrorCntAlarm	Set to TRUE if the current error count is not zero. This value can be alarmed.	Read-Only
BlockWrite.ItemErrorCntLast	The error count immediately prior to the current error count.	Read-Only
BlockWrite.ItemErrorCntLastEnd	The last time the error count returned to zero. The date format reflects the current locale setting for the operating system.	Read-Only
BlockWrite.ItemErrorCntLastStart	The last time that the error count changed from zero to non-zero, not including the most recent change to the error count. The date format reflects the current locale setting for the operating system.	Read-Only
BlockWrite.ItemErrorCntStart	The time that the error count most recently changed from zero to non-zero. The date format reflects the current locale setting for the operating system.	Read-Only
BlockWrite.StatsReset	Used to reset all statistics during run time.	Supervisory, User
BlockWrite.TransactionComplete	Set to TRUE when the transaction has completed.	Read-Only
BlockWrite.TransactionEnd	The time the last transaction ended. The date format reflects the current locale setting for the operating system.	Read-Only
BlockWrite.TransactionsCnt	The total number of transactions since the last statistics reset.	Read-Only
BlockWrite.TransactionStart	The time the last transaction started. The date format reflects the current locale setting for the operating system.	Read-Only
BlockWrite.TransactionStatus	Used to indicate the status of the transaction. Valid values are: InActive, Processing, and Completed.	Read-Only
BlockWrite.TransactionTimeAvg	The average amount of time required to process this group since the last statistics reset.	Read-Only
BlockWrite.TransactionTimeMax	The longest amount of time required to process this group since the last statistics reset.	Read-Only
BlockWrite.TransactionTimeMin	The shortest amount of time required to process this group since the last statistics reset.	Read-Only
BlockWrite.TransactionTimeoutAlarm	Set to TRUE if the transaction timeout has been exceeded.	Read-Only
BlockWrite.TransactionTrigger	If TRUE, the transaction will be started.	Supervisory, User
ConnectionAlarm	Set to TRUE if the OPCClient object can no longer communicate with the OPC Server.	Read-Only
ConnectionStatus	The status of the link between the OPCClient object and the OPC DA Server. Valid values: CONNNECTED, DISCONNECTED.	Read-Only
RestartAlarm	Set to TRUE if the number of attempts to start the OPC Server has exceeded the allowed maximum within the restart period.	Read-Only
RestartCnt	The number of times the OPC DA Server has been restarted during the restart period.	Read-Only
RestartReset	If TRUE, the restart count will be set back to zero. The RestartAlarm attribute (if enabled) will be turned off.	Supervisory, User
ScanGroup.Active	If the Active attribute is set to TRUE, and the ScanMode attribute is set to Active or ActiveAll, the object attempts to scan all of the data items in the group. If the Active attribute is set to TRUE, and the ScanMode attribute is set to ActiveOnDemand, the object attempts to scan data items in the group individually according to demand. If the Active attribute is set to FALSE, no scanning occurs, regardless of the setting of the ScanMode attribute.	Supervisory, User
ScanGroup.AliasDatabase	Used to store pairs of alias attribute names and the corresponding item references.	Read-Only
ScanGroup.ItemCnt	The total number of items in the group that are on advise by a client application.	Read-Only
ScanGroup.ItemErrorCnt	The current number of items that have been successfully added to this group and have data quality other than GOOD. This value is calculated.	Read-Only
ScanGroup.ItemErrorCntAlarm	Set to TRUE if the current error count is not zero. This value can be alarmed.	Read-Only
ScanGroup.ItemErrorCntLast	The error count immediately prior to the current error count.	Read-Only
ScanGroup.ItemErrorCntLastEnd	The last time the error count returned to zero. The date format reflects the current locale setting for the operating system.	Read-Only
ScanGroup.ItemErrorCntLastStart	The last time that the error count changed from zero to non-zero, not including the most recent change to the error count. The date format reflects the current locale setting for the operating system.	Read-Only
ScanGroup.ItemErrorCntStart	The time that the error count most recently changed from zero to non-zero. The date format reflects the current locale setting for the operating system.	Read-Only
ScanGroup.ItemUpdateCnt	The number of items whose values were updated during the most recent scan cycle.	Read-Only
ScanGroup.PingItem	The item quality of this item is checked on each scan to determine the scan group status.	Read-Only
SlowPollInterval	The slow poll interval, in milliseconds, in which the OPCClient object periodically retries the connection to the disconnected OPC DAServer after it goes into slow poll mode. This occurs after the "restart attempts" have been reached when certain connectivity problems, such as an unplugged network cable, prevent the OPCClient object from connecting to the OPC Server. When the OPCClient object achieves connectivity again with the OPC Server, it exits the slow poll mode and returns to normal operations. Slow polling is turned off if the value of this attribute is set to 0 (the default). The minimum value for slow poll is 6,000 milliseconds (6 seconds) to account for the time to confirm a broken network connection.	Supervisory, User

Related Topics

Alarm Aggregation Attributes

The following attributes are available for all Objects. If alarm aggregation is enabled on the Area, the following attributes aggregate their respective alarm status values for the Area, for all sub-Areas, contained objects, and their descendants assigned to the Area. If alarm aggregation is disabled, these attributes remain at their default values. Alarm aggregation attributes behave similarly to alarm aggregation of individual attributes.


Attribute	Description	Run-Time Access (Supervisory, User, Read-Only, None)
<Attribute>.AlarmCntsBySeverity	Array of counts of all alarms that are in UNACK_ALM, ACK_ALM, or UNACK_RTN states on the object, aggregated by severity levels 1-4.	Read-Only
<Attribute>.AlarmMostUrgentAcked	TRUE (default) indicates that no alarms are in the InAlarm state or waiting to be Acked. A value of TRUE also indicates that the most urgent alarm(s) on the object and its descendants in the InAlarm state have been acknowledged, whether or not they are currently InAlarm.	Read-Only
<Attribute>.AlarmMostUrgentIn Alarm	FALSE (default) indicates that no alarms are in the InAlarm state or waiting to be Acked. A value of FALSE indicates whether the most urgent alarm(s) on the object and its descendants are in the InAlarm state, whether or not they have been acknowledged.	Read-Only
<Attribute>.AlarmMostUrgentMode	The AlarmMode of the most urgent alarm(s) on this Object and its descendants. If no alarms are in the InAlarm state or waiting to be Acked, the value is the same as the AlarmMode for the Object.	Read-Only
<Attribute>.AlarmMostUrgent Severity	Severity level expressed as an integer 1-4 of the most urgent alarm(s) on the object and its descendants. If no alarm is in the InAlarm state or waiting to be Acked, the value is 0 (zero).	Read-Only
<Attribute>.AlarmMostUrgent Shelved	The Shelved status as a Boolean value for the “most urgent” alarm(s) on this Object and its descendants. A value of FALSE indicates that no alarms have been Shelved for the "most urgent" alarm(s) on this Object and its descendants.	Read-Only

Related Topics

Alarm Attributes

If an alarm attribute is enabled, then the following additional alarm attributes become available. None of these attributes can be alarmed.


Attribute	Description
<Attribute>.Acked	Used to specify whether an alarm has been acknowledged. This attribute is updated when the AckMsg attribute is set. This attribute is always set to FALSE when a new alarm condition is detected (when the InAlarm attribute changes from FALSE to TRUE).
<Attribute>.AckMsg	The operator comment at the time the alarm is acknowledged. Any received text is stored, and the Acked attribute is set to TRUE. Also, the TimeAlarmAcked attribute is set to the current time. The maximum length is 256 characters.
<Attribute>.AlarmMode	The current alarm mode setting. Valid values are: Enable, Disable, Silence.
<Attribute>.AlarmModeCmd	The command to set the alarm mode. Valid values are: Enable, Disable, Silence.
<Attribute>.Category	The category of the alarm. The label of each alarm category is fixed.
<Attribute>.DescAttrName	The description of the alarm. The description must be of type String or InternationalizedString, with a maximum length of 329 characters. The DescAttrName attribute can contain a static alarm description or a reference to another string attribute within the same object containing the alarm description. The reference must be in the form: "me.AttrName". If the reference is invalid, the actual reference string is used for the description. If nothing is supplied for the DescAttrName attribute, the object’s ShortDesc attribute is used at run time.
<Attribute>.InAlarm	The alarm state. This is exactly the same as the attribute in the host primitive that represents the alarm condition, except when the alarm state is disabled, in which case, InAlarm is set to Off, regardless of the actual condition state. The quality is set during execute to the quality of the attribute, except when the alarm is disabled, in which case the quality is always GOOD.
<Attribute>.Inhibit	If true, the alarm is disabled. This attribute is intended to be written to by a script, a user, or an input feature. Only the individual alarm is disabled. No other alarms are disabled in the same object or in any objects that are assigned to or contained by this object.
<Attribute>.Priority	The value for the urgency of the alarm. Valid values are 1 through 999, with 1 being the most urgent.
<Attribute>.TimeAlarmAcked	The timestamp indicating the last time this alarm was acknowledged. The date format reflects the current locale setting for the operating system.
<Attribute>.TimeAlarmOff	The timestamp indicating the last time this alarm (as represented by the InAlarm attribute) went off. The date format reflects the current locale setting for the operating system.
<Attribute>.TimeAlarmOn	The timestamp indicating the last time this alarm (as represented by the InAlarm attribute) went on. The date format reflects the current locale setting for the operating system.