OPCIS System UDCs

Tables > Uniform Data Codes > System UDCs > OPCIS System UDCs

OPCIS System UDCs

OPCIS Group status points serve several purposes, including:

They can be used to monitor statistics of the OPC server, OPCIS groups, and the OPCIS itself. Items that can be monitored include status of the OPC server, its start time, values received, group update rates (configured and actual), number of OPCIS groups, etc.
They can be used to control the update rate of an OPCIS Facility Group, force health checks, reregister points, and to get all values for a group.

An OPCIS Group status tag is just like any other tag in the PNT insomuch as it can be configured for alarms, notifications, and history. The properties that make an OPCIS Group Status tag unique are its facility (the name of the OPCIS group or the OPCIS) and its OPCIS-specific UDC. These UDCs are described below in the Group Activity, Group Control, and Group Status tables.

An OPCIS has at least one group — the default group. The facility of this group is OPCDEFAULTGROUP. OPCIS Group Status Points can be added for the default group or any custom group.

See the following subsections for more information:

Assorted
Group Activity
Group Control
Group Status

For general information about system UDCs, see System UDCs.

Assorted

The following UDCs provide system-level information.

UDC	UDC Name	Description	Point Type
SYOPCGSRT	OPC Server Data Request Time	The elapsed time, in MS, when retrieving data synchronously from the OPC server.	Analog Input
SYOPCPRQS	OPC Process Queue Size	Number of entries in the update processing queue of the OPCIS. This can be useful when measuring the performance of the OPCIS.	Analog Input
SYOPCPWQP	OPC % Pushes Waited	The percentage of total queue entries that had to wait to be added to the update processing queue because the queue was full. This can be useful when measuring performance of the OPCIS.	Analog Input

Group Activity

The following UDCs provide system-level information. These points monitor group activity. These points are automatically added by the OPCIS. The Facility of the points is: SITE_SERVICE.

Example

MYSITE_OPCIS

UDC	UDC Name	Description	Point Type
SYOPCSGAC	OPC Groups Active	Number of groups active in the OPCIS.	Analog Input
SYOPCSGCT	OPC Group Count	Number of groups defined in the OPCIS.	Analog Input
SYOPCSGNC	OPC Groups Not Connected	Number of groups not connected in the OPCIS.	Analog Input

Group Control

The following UDCs provide system-level information. These points can be used to control an OPCIS Facility Group via the use of a setpoint command. The Facility of a tag is its group name.

Example

OPC30SEC

UDC

UDC Name

Description

Point Type

SYOPCGCTL

OPC Group Control

This point triggers an update, forces a health check, or reregisters the group with the OPC server. Options for the trigger are:

0 = None

1 = Read all values

2 = Health check

3 = Register group

Enumeration table is OPCGCTL.

Enum Output

SYOPCGDEF

OPC Group Definition

Point configuration attributes for the OPC Group Definition tag define the information about the group, while the value of the tag defines the update rate of a group. The group point attributes described below will take precedence over OPC service configuration file keyword settings.

The point configuration attributes that have special meaning for an OPC Group Definition tag are General 1, Table Driven 1, Table Driven 2, Table Driven 3, and External ID. These attributes are configured on the Application and Point Reference pages of the point configuration record:

Attributes	Description
General 1	Many OPC servers initialize tags to a sentinel value (for example, -9999.99) that does not represent a true tag value. Set the General 1 property to a numeric value that should be ignored. When a tag with this value is received from the OPC server, it is marked as unreliable but the OPC value is not stored (the previous value is retained).
Table Driven 1	The Table Driven 1 property is used to indicate what to do with the value of an OPC tag with OPC Quality flags that indicate an error. The default behavior is to mark as unreliable and save the value from the OPC server. If set to OPCBADIGNR and an unreliable value is read, it will be discarded and the previous value is retained. If set to OPCBADSTR and an unreliable value is read, it will be stored.
Table Driven 2	The Table Driven 2 property specifies whether the OPC server is to retrieve data from the cache or the device. This applies to all synchronous communication. This attribute provides the functionality of the OPC_SYNC_IO service configuration file keyword at the group level. If set to OPCSYNCCCH, the OPCIS will sync IO via the cache. If set to OPCSYNCDEV, the OPCIS will sync IO via the device.
Table Driven 3	The Table Driven 3 property defines the type of communications between the OPCIS and the OPC server. This attribute provides the functionality of the OPC_IO_TYPE service configuration file keyword at the group level. If set to OPCIOASYNC the OPCIS will use asynchronous IO. If set to OPCIOSYNC the OPCIS will use synchronous IO.
External ID	The External ID property can be used to specify the server and machine name for the OPC group when linking points to an external OPC server. The format is: *server_name=<server>; machine_name=<machine>*

The value of the OPC Group Definition tag indicates the OPC group update rate:

A value of 0 triggers suspension of updates to all tags in the group.
A value of 1 triggers the use of the update rate defined by the service’s configuration file keyword OPC_MAX_UPDATE. This is the default value.
All other values represent the update rate in milliseconds (recommended minimum rate is 1000 ms). If communications are synchronous, the rate is the data retrieval rate. If communications are asynchronous, the rate is the maximum rate at which the OPC server can push values to the OPCIS.

Note: Deleting an OPCIS group's SYOPCGDEF point causes that group to use the default group settings from the .cfg file.

Analog Output

SYOPCWQS

OPC Group Write Queue Sz

The value of the OPC Group Write Queue Sz point represents the current number of items in the OPC write queue, which queues requests to write values to the associated OPC server.

As with the OPC Group Definition point, the General 1 property on the Application page of the point configuration record carries special meaning for this tag and defines information about the group. The General 1 property is used to control the maximum write queue size of the OPC group to which the point is added.

The default value is 1000. Set the General 1 property to another numeric value to change the size of the queue. Every change to the point will be logged in the OPCIS.

Analog Output

Group Status

The following UDCs provide system-level information. These points monitor statistics of an OPCIS Facility Group. The Facility of a tag is its group name.

Example

OPC30SEC

Initial Value

When adding OPCIS Group status points, one property to be aware of is the Initial Value property. This property determines if the tag has a value when the service starts. This is particularly important for a Group Definition tag (SYOPCGDEF), since this tag is used to specify the group update rate.

Note: The recommendation is to use an Initial Value type of Restore or Specified Value. Restore will persist the value from the last shutdown, or if no value is available it will use the value in the Value box. Specified Value will always use the value in the Value box.

Be aware that if you change the group update rate in run-time using a setpoint command and the Initial Value is Restore, the new rate will persist when the service is restarted. If you use Specified Value, the new rate will not persist. The update rate will be returned to the Specified Value when the service is restarted. To permanently change the update rate of a Control Definition Point that uses a Specified Value you must edit the Initial Value in the PNT.

It may be desirable to use a Specified Value with some Group status points.

Example

Setting the Group Active (SYOPCGACT) to 0 (Inactive) when the service starts.

UDC	UDC Name	Description	Point Type
SYOPCCONN	OPC Group Connected	Indicates whether the OPC group connected or not.	Analog Input
SYOPCGACT	OPC Group Active	OPC Group Active. OPC group active (via health check or configuration change). 1=Active; 0=Inactive.	Digital Input
SYOPCGDBND	OPC Group Deadband	OPC group dead band in percent (via health check or configuration change).	Analog Input
SYOPCGICT	OPC Item Count	Number of items in the group.	Analog Input
SYOPCGIFL	OPC Item Fail Count	Number of items in the group that were rejected by the OPC server.	Analog Input
SYOPCGRATE	OPC Group Actual Rate	OPCIS Facility Group actual update rate in milliseconds (via health check or configuration change). Actual may differ from specified due to OPC server configuration.	Analog Input
SYOPCGTBS	OPC Group Time Bias	OPC Facility Group time zone bias in minutes (via health check or configuration change).	Analog Input
SYOPCGTIM	OPC Group Last Comm Time	Time group last communicated with OPC server (includes data and health check).	String Input
SYOPCGUCT	OPC Group Last Update Ct	Number of group values received in last update.	Analog Input
SYOPCHBAND	OPC Server Bandwidth	OPC server bandwidth (via health check).	Analog Input
SYOPCHBLD	OPC Server Build Number	OPC server build number (via health check).	Analog Input
SYOPCHCT	OPC Healthcheck Time	Time on OPC server when health check was performed.	String Input
SYOPCHST	OPC Server Start Time	Time OPC server was started up (via health check).	String Input
SYOPCHSTAT	OPC Server State	OPC server state (via health check). Enumeration table is OPCHSTAT.	Enum Input
SYOPCHUPT	OPC Health Last Upd Time	Last OPC time data was sent before health check performed (last update time).	String Input
SYOPCHVEND	OPC Server Vendor Info	OPC server vendor info (via health check).	String Input
SYOPCHVMAJ	OPC Server Version Major	OPC server major version (via health check).	Analog Input
SYOPCHVMIN	OPC Server Version Minor	OPC server minor version (via health check).	Analog Input