DSC Module Glossary

A
ACK (Acknowledge)	The sequence action that indicates recognition of a new alarm.
alarm	An abnormal process condition. In the LabVIEW Datalogging and Supervisory Control (DSC) Module, an alarm occurs if a shared variable value goes out of its defined alarm limits or if a shared variable has bad status.
Alarm Summary	A display of shared variables currently in alarm, or a display of shared variables previously in an unacknowledged alarm state that have returned to a normal state.
B
bad status	An indication that the value associated with a shared variable is invalid. A bad status might occur for several of reasons, for example, a hardware read error occurred.
batch process	A process or production run that results in a batch of logged data, also known as a data set.
C
Citadel	A database for storing historical shared variable values.
D
data item	A channel or variable in a real-world device that is monitored or controlled by a device server.
data set	A group of shared variable values logged together as a set during a specified period of time.
DataSocket	DataSocket is both a technology and a group of tools that facilitates the exchange of data and information between an application and a number of different data sources and targets. It provides one common API to a number of different communication protocols.
device server	An application that communicates with and manages a peripheral hardware device such as a Programmable Logic Control (PLC), remote I/O device or plug-in device. Device servers pass shared variable values to the Shared Variable Engine in real time.
DSC	Datalogging and Supervisory Control.
dynamic attributes	Shared variable attributes that do not require the Shared Variable Engine to be restarted when they are edited or reconfigured. Examples of dynamic attributes include enabling logging operations, alarm attributes, and some scaling attributes. See also static attributes.
E
Engine	See Shared Variable Engine.
H
historical trend	A plot of data (values versus time) showing values that were previously acquired in the system or logged to disk.
host access	Controls whether a particular computer can access data on your computer, no matter who is logged on that computer.
Human Machine Interface (HMI)	A graphical user interface for the user to interact with the DSC Module system.
I
ID shared variable (data set)	When logging data sets, the ID shared variable for each data set denotes a particular data set and the time during which the data set run took place.
input/output (I/O) Group	A set of related server items, all of which share the same server update rate and deadband.
L
LabVIEW Datalogging and Supervisory Control Module Run-Time System	An execution environment for applications created using the DSC Module development system.
log deadband	The range through which a shared variable value must change before the Shared Variable Engine logs it to a Citadel historical database.
log resolution	The smallest change in a shared variable value stored in the Citadel database.
Logos	A proprietary National Instruments networking protocol, installed on the computer when you install the DSC Module.
M
Man Machine Interface (MMI)	See Human Machine Interface (HMI).
memory shared variable	A shared variable not connected to a real-world I/O point. Use memory shared variables for user-defined calculations.
O
ODBC	Open Database Connectivity. A standard developed by Microsoft, it defines the mechanisms for accessing data residing in database management systems.
OPC	OLE for Process Control. A COM-based standard defined by the OPC foundation that specifies how to interact with device servers. COM is a Microsoft 32-bit Windows technology.
P
proxy user	You can specify a proxy user account as a way to handle unrecognized access requests for data.
Published Variable Monitor	A National Instruments utility you can use to view the current value, status, and alarm state of a shared variable.
R
real-time trend	A plot of data (values versus time) that is updated as each new point is acquired in the Shared Variable Engine.
S
SCADA	Supervisory Control and Data Acquisition.
shared variable attributes	Parameters pertaining to a shared variable, including its alarm, limits, or engineering units. Configure shared variable attributes in the Shared Variable Properties dialog box.
Shared Variable Engine	The software service that maintains all shared variable values and alarm states and runs as a separate process, independent of the HMI application.
shared variable group	A set of shared variables primarily used for reporting and acknowledging alarms. A shared variable can be associated with only one shared variable group. All shared variables belong to the group <ALL> by default.
shared variable status	A shared variable attribute that determines the validity of a shared variable value. A negative status represents an error, a positive status represents a warning, and a status of zero represents a good shared variable value.
SQL	Structured Query Language.
static attributes	Shared variable attributes that require the Shared Variable Engine to be restarted if they are edited or reconfigured. Examples of static attributes are general attributes and I/O connection attributes, such as server, device, or item. See also dynamic attributes.
system developer	The creator of the application software to be executed in the the DSC Module Run-Time System.
system errors	Errors that happen in the the DSC Module Run-Time System, like a server going down. LabVIEW displays system errors a dialog box.
system events	Events that occur in the the DSC Module Run-Time System, like an operator logging on or a utility starting.
T
timestamp	The exact time and date at which a shared variable value was sampled. Shared variable values are stored with their time stamps in the Shared Variable Engine.
trend	A view of data over time. Trends can display real-time or historical data.
U
update deadband	The range through which a shared variable value must change before it updates in the Shared Variable Engine.

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