I am working with an AF Analytics service with escalating scheduling lag issues.

We've been tracing these lag issues through the various calculation groups running on the service, and have noticed that all of our worst-performing analyses are Naturally scheduled with the suffix "(Rank:0)" through to "(Rank:5)". **1) What precisely does Rank signify?**

My starting assumption was that these indicate dependencies upon other calculations, but then I've observed that my highest *AverageLagms *results are for Rank:0 calculations, and then sequentially Rank:1, Rank:2 etc each have lower worst-performers than the previous Rank. So it seems counterintuitive that if my few 5's are those with five layers of dependencies, that they would have the least lag accruing.

In general we have already fixed our worst-performers which were making liberal use of expensive functions - most of these ones left in my list are legitimate calculations happening at (relatively) sensible natural intervals, and so I have reservations about putting them all to Fixed periods unnecessarily.

Regardless of their cause, **2) Are there particular Analysis Service Configuration options which govern this Ranking behaviour** **and could help finetune the performance of these groups?**

Many thanks

Steve

Hi Steven,

Which version of Asset Analytics are you running? I'm asking as the statistic reporting as changed considerably over the years.

Your assumption is correct, the rank signifies the level of dependency.

In terms of lag, there are different types of lag, notably SchedulingLag and EvaluationLag. The AverageLagMilliSeconds you are seeing at the analysis level is a report of the EvaluationLag. When the analysis triggers it takes time for the evaluation to happen and this time is considered EvaluationLag. The higher rank analyses might be performing better than the lower rank analyses and this is why the AverageMilliSeconds lag you are seeing is lower. If you have a look at the LastCompletedRequestStatistics for that analysis group, I suspect that you will see a high SchedulingLag. SchedulingLag reports the amount of time between when the analysis should have been triggered and when it was actually triggered. When lower rank analyses aren't performing well, they delay the execution of higher rank analyses or in other words they delay the scheduling of higher rank analyses.

In terms of service configuration, there are none that govern the ranking behavior. That being said there are some configuration parameters that could be changed to better the performance of your analysis service in general.

In 2018, there are significant enhancements done in terms of performance of dependent analyses. The release is due at the end of Q2 2018: https://techsupport.osisoft.com/Products/Product-Roadmap

I hope this helps clear things up!

Thanks,

Seb