Friday, March 9, 2012

FactoryTalk View Machine Edition Data Logging Best Practices.

FactoryTalk View Machine Edition Data Logging Best Practices - Understanding Data Logging

This information is applicable only to the native Data Logging of RSView Machine Edition and does not apply to the DataStore or DataStore Plus ActiveX controls.
NOTE: The following information applies to version 5.x and older terminals. Testing has shown that a current, typical application will run faster and have less memory constraints on the 6.x platform.

What Does the RSView ME Data Log Model Do?

  • Logs tag data to a storage file during runtime
  • Historical Trending

Data Log Model (Design Time)

  • Studio allows the creation of multiple Data Log Models. However, only 1 Data Log Model can be configured during runtime.
  • Maximum number of tags allowed in a model is 100:
    • The model will not log data for string tags, array tags, parameters or expressions, and you cannot use tag placeholders in your data log model.
    • External Compact flash path is configured as \Storage Card2\log.
    • USB drive path is configured as \USB Storage\log.

      NOTE
      : Only 2711P-RCx, which is the RA Compact Flash card have been tested/supported.
  • Data Log Model (Runtime)
  • The data log will run as a continuous background task.
  • Once the data log starts, it cannot be stopped during runtime by the operator.
  • If the data log fails on startup, it will never start. A warning message is logged to diagnostics when the data log starts or fails.
  • If diagnostics is not configured, you have no indication whether the data log started or not.
  • If a write fails to a remote data log or external compact flash card, the data log will stop and never re-start. For example, if the CF card is removed while data logging, it will try to reconnect 3 times within a few seconds and stop if not reconnected.
  • RSView ME doesn't support dynamic log file creation during runtime.
  • The DataStore Plus ActiveX does allow dynamic log file creation for Versa View CE platforms.
  • For additional information, refer to Technote Answer 35155 - DataStorePlus ActiveX Control for RSView Machine Edition.
  • Best practices for a Panel View Plus 400-600 terminal is to data log to a external CF card or remotely.
  • The Panel View Plus 400 – 600s are limited to 32 Mb for internal storage memory.
  • The data log file can consume a max of ~4.5 Mb for 300,000 data points

Viewing Data Log Files

 Remote Data Logging

  • The remote PC is require to be a member of a Domain. Remote Data Logging to a workstation will not work.
  • The Panel View Plus/Versa View will be prompted to authenticate when the data log initiates. 
  • Pre-authentication can be done from the ME configuration screen.
  • RSView ME does not accept specific IP addresses of any remote computer. For example: Custom Logging Path “\\10.10.10.10\logs” will not work. A name resolved from the Domain controller “\\MY_PC\logs” will work.

Why Remote Data Log?

  • The Log files are easily available for viewing on the PC.
  • Data log memory consumption occurs on the PC, not the PVP/VVCE terminal.

Log Triggers

  • Fastest log rate possibly is 100 ms.
  • Logging too fast can cause performance related issues. For example, logging 100 tags as 100ms will cause a buffer overflow.
  • Data logging is a background task. Best practice is logging at the slowest possible rate desired by the process being monitored.
  • Increase datalog time to at least 300ms if logging 100 tags or reduce tag count to 40.
  • On change, logging will update based on any tag configured in the model.

Data Logging Runtime Performance

Performance Considerations

  • The max number of data points possible is 300,000 records.
  • FIFO principal is used on the created Data Log File.
  • The max number of data points will consume ~ 4.5 Mb of internal storage space. The data log write buffer will also consume 4.5 MB of RAM.
  • Limit the maximum number of data points being logged to what is required.
  • RSView ME will write data every 30 seconds to the data log. If the buffer fills up before 30 seconds it will write data to the log immediately.
  • Data Log Memory is allocated on startup of the application.
  • Fast logging rates can affect overall application performance.
  • The HMI is required to Multi-task by data logging and update display information.
  • Additional background tasks include Alarming, Global Connections, and Information Messages.

CPU Utilization

As the number of data points logged increases, the terminal CPU utilization at the time of opening a Graphic Display containing a Trend object connected to a Data Log will increase along with the time to open the Graphic Display. Typical CPU utilization for a 300,000 record Data Log is around 20%. Graphic Display opening time is around 15 seconds.

Best Practices for Optimizing Performance & Memory

Data Log Model (Design Time)

  • Limit data logging to required tags only.
  • Limit the maximum number of data points being logged to what is required.
  • Log tag data at the slowest possible rate desired by the process being monitoring.

Data Log Model (Runtime)

  • Panel View Plus 400-600 terminals should data log to an external CF card or remotely.
  • Remote data log whenever possible.
  • Configure all application to display warning messages in Diagnostics to alert the operator when the data log starts or stops.

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