2.1.6. Device Data Item: Memory Usage Options| CIMPLICITY 11.1 Documentation

Delay Load

Delay loadis available in point configuration to help conserve memory.

The point is not loaded into memory in the Point Manager or Devcom at project startup. Rather, the point is loaded into memory only when it is demanded by an application. When the point ceases to be demanded it will be unloaded from memory in the Point Manager and Devcom.


Class: Data item configuration
Instantiation: Point properties result.
Benefits and disadvantages: Delay Load

Class: Data item Configuration

When Delay Load is checked in a Data Item dialog box

Just-In-Time is disabled.
A scan rate is required.

Instantiation: Point Properties Result

Delay Load is read/write in the object's Point Properties dialog box, whether or not it is checked in the Data Item dialog box.

Benefits and Disadvantages: Delay Load

Delay Load benefits and disadvantages are the same whether the point is included in an instantiated object or is created in the project's Workbench. They are as follows.


Benefits	Disadvantages	Non-Supported Functions
Loaded when needed No memory usage until point is loaded Written to point database Available in point list Definition can be modified	Slower access Configuration updates can be lengthy on larger systems Trigger settings and Alarm options are not available	Trend buffering Alarming Cannot be used within another point's configuration, e.g. Safety point, Trigger, Availability Trigger point, etc. Cannot be used in a calculation point equation

Just-In-Time

When Just-In-Time (JIT) is checked, data item instantiated point configuration is created by the Point Manager when an application requests it.

When the application is done, the data item is removed from the Point Manager. It is not written to the point database.

JIT Data Items can be used in:

CimView,
Point Control Panel,
Trending, and
Scripting.

Important: Change approvalis not supported with Just-In-Time points.


A	Class: Data item configuration
B	Instantiation: Point properties result.
C	Benefits and disadvantages: Just-In-Time

Class: Data Item Configuration

When Just-In-Time is checked:

Delay Load is disabled.
A scan rate is required.

Instantiation: Point Manager Result

An instantiated object does not list a point for the Just-In-Time data item in the Workbench.

Example

The data item VLVBP in a class TANKR was configured to be a Just-In-Time point. It is not included in the instantiated point list when an object is created from the class.

Benefits and Disadvantages: Just-in-Time

Just-In-Time benefits and disadvantages are as follows.


Benefits	Disadvantages	Non-supported Functions
Created on demand when needed No memory usage until point is created Project uses less disk space Point database is reduced	Not available in point lists Slowest access Device points only Does not reside in point database Definition cannot be modified Exclusive to classes Trigger settings and Alarm options are not available Note: Are not recommended for points that are accessed often.	Trend buffering Alarming Attribute set Analog deadband Cannot be used within another point's configuration, e.g. Safety point, Trigger, Availability Trigger point, etc. Cannot be used in a calculation point equation Cannot use another point within its configuration, e.g. Safety point, Trigger, Availability Trigger point, etc. Cannot be marked as an enterprise point.

Standard Memory Load

When Delay Load and Just-In-Time check boxes are clear in a Data Item dialog box, an instantiated point has standard memory usage.

Standard memory load benefits and disadvantages are the same whether the point is included in an instantiated object or is created in the project's Workbench. They are as follows.


Benefits	Disadvantages	Non-supported Functions
Accessible any time Quick access Written to point database Available in point list Definition can be modified	Uses memory in point database Project uses more memory Configuration updates can be lengthy on larger systems	None???all functions supported