Niagara virtuals cache (Virtual Policies)

Starting in AX-3.7, the NiagaraNetwork in any station has a “Virtual Policies” container slot (Figure 122).

Figure 116. Example Virtual Policies container expanded in Supervisor station to show “Cache” child

For a Supervisor’s NiagaraNetwork, or for any station’s NiagaraNetwork that uses Niagara virtuals, this provides access to cached data on virtual components. For any other station (typically most JACE stations), the Virtual Policies container is unused.

From the NiagaraNetwork’s property sheet, expand this container to see the available configuration properties and contained “Cache”. Typically, default property values are appropriate—for more details see Virtual Policies (Cache) properties.

Double-click the Cache component for its default Niagara Virtual Cache View.

Figure 117. Niagara Virtual Cache View of NiagaraNetwork’s cache (with station select drop-down)

As shown in Figure 117, this tabular view lists cached virtual ords, with a “station select” control at the top. Click row(s) to select, where bottom buttons let you “Select All”, or “Remove” any selected.

Double-click a row for a popup dialog showing details on data in the virtual cache (Figure 118).

Figure 118. Double-click row in Niagara Virtual Cache View for cached details on virtual component

As shown, cached data includes a target’s slot ord along with information on its facets and slot flags.

In the case where a recent facets or slot flag change has been made to the target of a virtual component, but is not properly reflected in Px access of it, you can check it here. If necessary, you can then remove it from the virtual cache, so it can properly update and be added back in the cache upon next access.

The ““Select All” is available too, which can be used “NiagaraStation-wide” to remove all cached data. In addition, note the Cache component has a right-click “Clear” action, accessible on the NiagaraNetwork’s property sheet (Figure 119).

Figure 119. Clear action on Virtual Policies > Cache component, from NiagaraNetwork property sheet

Clear removes cached data for virtual components across all NiagaraStations in the NiagaraNetwork.

Virtual Policies (Cache) properties

In most cases it is recommended you leave configuration properties at defaults, as shown in Figure 120.

Figure 120. Virtual Policies expanded in NiagaraNetwork property sheet

Properties and slots of the Niagara Virtual Cache Policy are as follows:

Cache Type

Cache type has two fields as drop-down choices, with currently the first fixed at niagaraVirtual, and the second as either:
- DefaultNiagaraVirtualCache — (default), so that ords and associated data from accessing virtual components is cached in memory. Also see Gateway memory cache and Refresh action.
- NullCache — Nothing is cached. In this case, virtual component access results in more network traffic and graphics will be slower to load.
Cache

Cache is the component representation of virtual cache data, with the default “Niagara Virtual Cache View” (see Figure 117). Configuration properties include:
- Persist Cache — (default is true) where some slot data for virtual components is stored persistently in cacheN.nva file(s) in the specified “Cache Directory”. Typically these file(s) are created upon station shutdown. If set to false, the virtual cache is not persisted.
- Cache Directory — The file ord to the folder in which cacheN.nva file(s) are created when “Persist Cache” is true. The default ord is file:^niagaraDriver_nVirtual

Note persisted virtual cache files can also be examined in Workbench by double-clicking for a “Nva File View”, as shown in Figure 121.

Figure 121. Workbench provides a default “Nva File View” for persisted Niagara virtual cache files.

In the example station shown above there is only one virtual cache file. However, a large Supervisor station will typically have multiple virtual cache files.