Power BI – Live connection vs. Import, comparison and limitations

by jirineoral Regular Visitor ‎10-31-2016 02:13 PM - edited ‎10-31-2016 02:13 PM

Some of the data sources have option both to import data as well as use live connection. But there is no easy method to change it once you already built your report. So you should rather carefully decide which method you’re going to use upfront. To make this decision right, it is good to know limitations of each method. Purpose of this blog post is to cover these limitations.

First what kind of license are you going to need? If you’ll use live connection, you’ll need Pro license for all end users consuming report/dashboard. If you’ll import data from on premises data source through gateway, you’ll need Pro License again. If your data are accessible without gateway, but you want to refresh them more often, then once a day, Pro License is required too. If you want to stay with free Power BI license, you’ll need to use data Import method only and avoid on premises data sources, refresh data maximally once a day.

 

Data import

Data import can be used against any data source type. Current Power BI service limitation published file size is 1 GB. Data are loaded to file using column store compression. If you’ll read for report purposes just data required for usage in visuals this is not limiting too much. Even with Power BI Pro license you are limited to 8 refreshes per day. Times can be scheduled either at full hour or half past full. Scheduled time is approximate. When will refresh actually happen depends on service utilization. If you need to refresh data, more often consider using live connection. When using import, data are stored in Power BI file/service. Therefore, there is no need to setup permissions on data source side (service account for load is enough) and you can share data publically or with people outside organization. On the other hand, all data are stored on Power BI. So if you have requirement for Row Level Security, you need to implement it on Power BI side. If you need same logic applied for multiple reports, you have to duplicate it in all the reports. Same applies to calculations, if you need same measure in multiple reports, you need to recreate it every time.

 

Live connection

There are more limitations for live connection in place. It doesn’t work against all data sources. Current list can be seen here https://powerbi.microsoft.com/en-us/documentation/powerbi-refresh-data/#live-connections-and-directq...

You are also limited to just one data source/database you selected. You can’t combine data from multiple data sources anymore. If you are connected to SQL Database, you can still create logical relationships between objects from that database as well as measures and calculated columns. When you are connected to SQL Server Analysis Services, you are limited just to report layout and even can’t make calculated columns or measures. When connected to SSAS, you could also reach some licensing limitations. Power BI issues DAX queries against SSAS and this isn’t supported in Standard edition of SQL Server before SQL Server 2016. When using live connection, users have to have access to underlying data source. This means you can’t share outside of your organization or publically. Other way around, when you set up security once, all reports using live connection to the same source have the same security model applied automatically. Similarly, you can prepare your data model carefully with all measures and calculated columns on data source side. All reports from the same data source can benefit of it. Refresh frequency is unlimited. Power BI simply shows data as they are in database. However, be careful using live connection against highly transactional OLTP systems. If you suffer from performance problems now, analytical workloads from Power BI won’t help it. Consider enabling features on data source side like Operational Analytics in SQL Server 2016.

 

Summary

Both methods have limitations, developer should be aware upfront. For import it is mainly refresh frequency, data size and necessity to duplicate same logic (calculations, security) in multiple reports. That could be helped by templates, but if you need to change logic of calculation, you need to change it in multiple reports again. For live connection, not all data sources are supported. If you pick one, then you’re limited just to that one data source for report. If logic is setup on source side, all reports can benefit. My personal preference is use live connection against SSAS models, have the model centralized and maintain logic in one place. For SQL Databases where I don’t have model, I prefer import and use Power BI as a model and vizualization.

Comments
by vrocca Regular Visitor
on ‎11-02-2016 11:26 AM

In case you do run into a scenario where you have to replace your data source, here's a quick walkthrough showing you how to go about doing it: http://www.victorrocca.com/how-to-replace-a-data-source-connection-with-a-live-connection-in-power-b...

 

by jirineoral Regular Visitor
on ‎11-03-2016 01:13 AM

Hi Victor, 

yes I know it is possible, but a lot of pain Smiley Happy Not just that you have to remap all fields, but also recreate all measuers and calculated columns. And in some scenarios you can't switch at all. For example if you combined multiple data sources by import and then you decide to switch to live connection. So it should be planned carefully upfront

Jiri

by vrocca Regular Visitor
on ‎11-03-2016 04:09 AM

Good point!

by Ermin Frequent Visitor
on ‎11-30-2016 04:54 AM

what are your expirience on scalabillity and prformance of the reports between import vs. direct query approach?

by jirineoral Regular Visitor
on ‎11-30-2016 05:15 AM

@Ermin generally speaking you you can reach a lot of limits using import method. Datafile size, number of refreshes, and recently we found out even query limits. So for scalable solution with larger datasets live connection is defenitively better approach. Just make sure, you're enterprise gateway doesn't have any connectivity issues neither internally nor externaly. 

Jiri

by juanglezmex New Member
on ‎12-01-2016 01:23 PM
Hello Experts,

I am new to Power BI, already do a graph in Power Bi Desktop, and download the APP on my cell, my question is how can I see in the Power BI APP the graph I made on my desktop?
by jirineoral Regular Visitor
on ‎12-01-2016 11:58 PM

Hi @juanglezmex,

publish your report from Power BI Desktop to Power BI Service, then login to your mobile app and in "my workspace" switch to reports. It should be there

 

Jiri

by sajid_siddiqui Visitor
on ‎03-08-2017 04:29 AM

Can we have a Live connection with SQL Server on Azure VM from Power BI ?

by sajid_siddiqui Visitor
on ‎03-08-2017 04:31 AM

Can we have a Live connection with SQL Server on Premise from Power BI ?

by jirineoral Regular Visitor
on ‎03-08-2017 05:01 AM

@sajid_siddiqui: Yes you can have live connection against SQL Server in Azure VM. You just needs to make sure, that connectivity and authentication works for you during development phase. When developing, you'll need to make sure, that you set up firewall rule for machine where you will develop using Power BI desktop. No need for set up after publishing to Power BI Service as far as I know. Also Azure VM will need to be in same domain, or you'll need to deal with UPN mapping after publishing.

 

Jiri

by sajid_siddiqui Visitor
on ‎03-15-2017 02:38 AM

thanks Jiri,

Is any idea how to achive column level security in Power BI.

For example some user can see some measures from Fact table and admin user able to see all measure from that Fact Table. 

by jirineoral Regular Visitor
on ‎04-03-2017 06:22 AM

Hi Sajid @sajid_siddiqui

This is not supported as far as I know. Even if it would, I'm not sure how would work if you referenced a column in chart and user didn't have permission on that column

 

Jiri