Administrator User Guide
AVEVA E3D™ Databases : Database Cache Service
Database Cache Service
The Cache Service stores a copy of project data on the local disk to improve performance where there is repeated reading of project data across a computer network. The cache must be active on the machine running the application, but the cache is shared by all applications and users running on that machine. If the Cache Service is not active then database access is via the network file system, as usual. Projects that are already stored on a local disk will not be cached.
Message Queuing (MSMQ)
Before the Cache Service can be used it is necessary to activate Microsoft Message Queuing (MSMQ) on the workstation. Refer to the Database Cache Service Installation Guide for further information.
Note:
The user must have Administrator rights to be able to activate MSMQ.
Managing the Database Service and Cache Storage
The Cache Service Management Tool is available to the user by selecting Cache Manager from the Start menu. It is used to check on the current status of the Cache Service, and to allow users of a workstation to manage the service, with particular emphasis on the local disk storage usage.
Using the Cache Service Management Tool the user can:
•
Delete selected cached projects from the cache folder on their local disk.
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Change the location of the cache folder. A new folder will be created and the contents of the old folder will be left intact.
•
Change the maximum disk usage proportion used by the Cache Service. If the disk usage exceeds this threshold then the Cache Service will not write any new cache data to the disk.
•
Change the time period, in days, after which cached projects that have not been accessed will be automatically deleted.
•
Activate, de-activate or reset the service. Note: This is not a full service restart.
Delete a Project from the Cache Storage
The cache storage folder contains a number of sub-folders, each representing a cached project. The full pathname of each project sub-folder is listed in the Cache Storage Control pane. The text pane is resized automatically to fill the available space in the window.
Cache storage space can be made available by manually deleting a cached project that is no longer needed, by selecting the appropriate cache storage sub-folder and clicking Delete. Projects can be identified using the cache sub-folder pathname:
<cache folder location>\<representation of network pathname of project folder>
The network pathname part is the UNC path of the actual project with backslash ('\') characters replaced with minus ('-') characters. For example, when using cache storage folder C:\Cache, the actual network shared project folder:
\\projectserver\projects\Test\tst000
appears in the Cache Service management tool as:
C:\Cache\--projectserver-projects-Test-tst000
Change the Cache Storage Folder location
To change the location of the folder used for cache storage click Browse to the right of the text box labelled Cache Path. A file browser is displayed and allows the creation of a new folder, or selection of an existing folder. It is also possible to type a file path directly into the text box. Changes are applied by clicking Save.
The Cache Service will create the specified cache storage folder if it does not already exist. The previously used cache storage folder is left intact; allowing it to be used again effectively in future if possible.
Control Maximum Disk Usage
The Cache Service maintains a disk usage threshold to avoid the cache using all available space on the volume which holds the cache storage folder. The Cache Service will not write any further cache data if the usage on the cache storage volume is greater than or equal to the specified threshold.
The Cache Service Management Tool provides information and control relating to this threshold in the Cache Service Configuration pane. Current cache disk usage displays the current proportion of space used in the volume containing the cache storage folder. The Stop caching threshold slider control displays the current setting of the disk usage threshold for the Cache Service. Moving this slider changes the threshold value. Changes are applied by clicking Save.
Auto-Purge
The Cache Service can automatically manage the space used in the cache storage folder by removing sub-folders for cached projects that have not been accessed using the service for more than a specified number of days, this is the auto-purge period.
The current setting of this period is shown in the text box labelled Purge unused caches after. The period can be changed by clicking on the up and down arrows to increase or decrease by one day, respectively, or by typing a whole number directly into the text box. Changes are applied by clicking Save.
An auto-purge period of zero indicates that the auto-purge facility is inactive such that cache storage sub-folders will not be removed automatically.
Cache Service Control
The current status of the Cache Service is displayed in the Cache Service Control pane. If the service is active and available then Caching Activated is displayed and coloured green.
If the service is not active then Caching Deactivate is displayed and coloured red.
If the service is not running then Caching Service unavailable is displayed.
By clicking on the coloured button the active status of the Cache Service is toggled between active and inactive which allows a user to de-activate the locally running Cache Service. The cache service is still running but while it is deactivated it will not fetch or store any cache data.
Clicking Reset service causes the service to reset its message processing without stopping or re-starting the service.
If the service is not running then it is not possible to activate it from the Cache Service Management Tool. The administrator needs to restart the service using Windows facilities: Control Panel > Administrative Tools > Services.
Monitor Database Cache Activity
The administrator can monitor the activity of the Cache Service using the Windows Performance Monitor Tool (Control Panel > Administrative Tools > Performance). The following performance counters can be added to confirm that tests are interacting correctly with the Cache Service:
AVEVACacheService: ClientsConnected
AVEVACacheService: PageStoreCount PageStoreRate
AVEVACacheService: CacheMissCount CacheMissRate
AVEVACacheService: CacheHitCountAllPages CacheHitRateAllPages
A graph scale of 10 is suggested for the ClientsConnected counter; graph scale 0.1 for each of the rate counters.
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