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Glossary (DSC Module)

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

E
engine See Shared Variable Engine.
EPICS Experimental Physics and Industrial Control System. A set of open-source software tools you can use to develop large, distributed control systems. EPICS also refers to the architecture of such systems, as well as to the collaboration group developing the related tools. Refer to the Argonne National Laboratory Web site for more information about EPICS and to download the latest version of EPICS.

H
historical trend A plot of data (values versus time) showing values that were previously acquired in the system or logged to disk.
Human Machine Interface (HMI) A graphical user interface for the user to interact with the DSC Module application.

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.
logging deadband The range through which a shared variable value must change before the Shared Variable Engine logs it to a Citadel historical database.
logging 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
Modbus An application-level messaging protocol that provides client-server communication between devices connected on different types of buses or networks.

O
ODBC Open Database Connectivity. A standard developed by Microsoft, it defines the mechanisms for accessing data residing in database management systems.

P
process Project libraries that LabVIEW deploys to the Shared Variable Engine are called processes. Making changes to a process or to a shared variable within a process without affecting the corresponding library is known as online configuration. Making changes to a library or to a shared variable in a library without affecting the corresponding process is offline configuration. If you use offline configuration to change a shared variable, you must redeploy the library to the Shared Variable Engine before you run any VI within the library so the Shared Variable Engine can update the shared variable in the process.
proxy user You can specify a proxy user account as a way to handle unrecognized access requests for data.

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
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
system errors Errors that happen in 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 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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