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Hello Everyone –

As this is the second in a series of six BIA blogs being developed by the NetWeaver BI RIG, I hope you continue to find value and provide comments. Prior to reading this blog, please consider reading the first blog, BIA Changes Everything, if you haven’t read it already, BIA BLOG Series, Part I: BIA Changes Everything!.

One of the first steps when preparing for a BIA implementation is to determine how many or which InfoCubes will use BIA. The number of InfoCubes will help determine the sizing of the BIA appliance you order. There are really two schools of thought when determining the number of InfoCubes:

  1. Put the entire environment in BIA. This can appear costly up front, however the performance gain, the decrease in DASD usage and the time removed from the nightly load window can significantly offset the up front costs of BIA.
  2. Only choose those InfoCubes whose query statistics show a large amount of time spent in the database or are the foundation for management cockpits or dashboards. To identify these InfoCubes, rely on the BI statistics queries which are delivered with BI Content. By using the technical name of the query, identify which spend large amounts of time doing data selection. In addition, you can execute queries in RSRT to further understand the performance. From RSRT, select the query and click on Execute + Debug. When the list of options appears, select Display Statistics Data and Do Not Use Cache. After the results are returned, click on the green “<–” button. This will bring you to the Statistics Data for Query Runtime page. Under the Event Text column, notice an event called Data Manager, this is equivalent to time spent in the database. BIA addresses queries with large amounts of time spent in the database. Secondly, by clicking on the Aggregation Layer tab, see what InfoCubes and aggregates are being used to execute the query. With a combination of these tools you can quickly identify which queries/InfoCubes should be targeted for BIA.

Go-live strategy – Like all other IT projects, a BIA implementation should actively involve the business users. With BIA especially, the enthusiasm which is generated by the business when they begin to see the performance improvements and the ability to see how much easier it is to meet service level agreements goes a long way toward a successful implementation. However, setting expectations is required. Keep in mind the majority of the query performance will come from those queries which spend long periods of time in the database. BIA will not provide much help for those queries whose time is spent in the OLAP processor.

Once the InfoCubes have been determined, decide on the strategy for activating BIA in a production environment. Provided testing in a DEV and QA environment are successful, your options are to activate all at once or use a staggered approach. Activating all at once provides all business users with immediate performance boosts and quickly shows signs of lowering TCO. If problems are identified for certain InfoCubes, with the flip of a switch, BIA can be deactivated. There is no long arduous task of turning BIA off. With the simplicity of this, it makes activating BIA for all InfoCubes very appealing.

With staggering the roll out of BIA to multiple InfoCubes the process takes much longer, performance gains in one area and not in others often lead to the business users questioning if BIA is working. Regardless of the method chosen, refer to OSS Note 1161525 to turn off BIA per user/query. This will allow you to turn on BIA but only have certain users access the index. This can be helpful when you roll out BIA by certain user groups.

You will also need to have a strategy for deactivating aggregates and removing secondary indexes on E and F fact tables. My recommendation is to go live with BIA and aggregates until IT and the business users are comfortable. Once this occurs, typically four to six weeks, begin turning the aggregates off and delete them. This will allow you to regain disk space as well as reduce the amount of time it takes to execute the change run. In addition, because queries will now be executed off of BIA, there is no longer as much of a need to maintain secondary indexes on the fact tables (exceptions are initial filling of BIA indexes, infosets, query has request ID as a characteristic, BIA is deactivated for the query containing virtual Infoobjects, 3.X queries that still use calculated key figures with “calculate before aggregation” proptery turned on, using open hub on the fact table and transferring data from one InfoCube to another dataprovider.) Often, the size of the indexes are as big as the fact tables themselves. This will allow you to recover additional disk space and speed up data loads because updates/inserts are no longer taking place. 

If the deletion of aggregates and indexes become part of your BIA strategy, it’s important to understand the potential impact if BIA for some reason becomes unavailable. If this should happen, queries will now execute against the fact tables with no aggregates or indexes, causing very slow query performance. That’s why these activities should be part of the strategy but executed when you’re comfortable with BIA.

BIA and Process Chains – In order for delta data loads to make their way from the Infocube to BIA, a process chain must be in place with the process type “roll up” at the end. This is the same process type used in a process chain to roll up aggregates. After identifying the InfoCubes you would like to send data to BIA, determine if the process chain already has a roll up step at the end. If it doesn’t, one needs to be added. This is a task which can be performed prior to the BIA implementation. Consequently, in the case where there are frequent deletions of requests from the Infocube or selective deletion of data from an Infocube occurs in the process chain, additional work will be required. These tasks will be further documented in the next blog in the BIA series, BIA Maintenance.

 

The next blog in the series will be entitled BIA BLOG Series, Part III: Checking Data Consistency with SAP NetWeaver BI Accelerator and will appear in SDN in the coming weeks.

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9 Comments

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  1. Anonymous
    You mention deletion of the secondary Indexes on the E and F Fact table (and keep them dropped)
    Can you just confirm that this is normal for a BI-A implementation
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    1. Josh Djupstrom Post author
      Hi Simon – This is certainly not required and is entirely based on whether companies are looking for additional TCO impact from BIA in addition to query performance. After the implementation of BIA, queries no longer execute off of the infocube but instead BIA. Therefore, the secondary indexes are not required, unless they are using the infocube for hub and spoke or transfering data from one infocube to another. By removing the secondary indexes, significant allocations of DASD can be reclaimed. In some companies, I’ve seen hundreds of gigabytes and even a terabyte reclaimed. There is some risk with removing the index however. If BIA should become unavailable, queries would be executed off of the infocube and with secondary indexes removed, query performance will be bleak. This is why I would only suggest doing this once BIA is stable within the installation, those maintaining it are comfortable doing so and the company is willing to assume additional risk to lower TCO. Based on my experiences, this option is not for every company.
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      1. Anonymous
        Many thanks for the reply.
        So in the theoretical scenario – the base infoprovider is actually acting as a “virtual” structure just to get the data into BI-A
        Interesting – because if I think this through to it’s logical conclusion – in time (hopefully) – there will be no need to load data into the cube and then into BIA we just go from the DSO into a BIA structure (that is if we a totally fail safe fallover BIA server)
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        1. Josh Djupstrom Post author
          That is absolutely correct! With the next release of SAP NetWeaver BI, a hybrid InfoProvider is introduced. This will allow data to be sent directly from a DSO to BIA without having data persist in the cube. This is another example of lowering TCO with BIA. If you choose, no longer will you need to load data into a cube and onto BIA. You’ll be able to go directly from a DSO to BIA, removing time from the load window as well as lowering DASD levels. Again, this is not mandatory but will become an option with the next release. Thanks for inquiring. You brought up a good point.

          Regards,

          Josh

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            1. Josh Djupstrom Post author
              Hi Vitaliy

              The Hybrid provider will work with standard DSOs only. There currently are a few pilots underway working with Write-Optimized DSOs and BIA. In these cases a virtual infoprovider is created to tie in the WO DSO and the BIA index. Providing things continue accordingly this functionality may also be available in the next SAP NetWeaver BI release as well.

              Hope this helps.

              Regards,

              Josh

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  2. Witalij Rudnicki
    Hi Josh,

    Good weblog! I would wish it to be even bigger, containing more from the RIG experience of BIA implementations.

    For the moment, I would like to add to Indexes discussion. So far I never recommended my customers to drop secondary indexes (I hope we are on the same page, and you are talking about system-created bitmap indexes on each column of F/E tables), although discussed this with Jens in the past. Is it a case for every of your customer?

    I believe it is importnat to mention that secondary indexes (and up-to-date DB statistics) are important during initial filling of BIA indexes.

    As well I would like to add couple of more cases when BIA is not used, that BIA customers have to be aware of:
    1) in InfoSets,
    2) when query has RequestID as a characteristic (although usually it is IT scenario, not business really),
    3) when BIA is deactivated for the query containing virtual InfoObjects.

    Regards,
    -Vitaliy
    HP

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    1. Witalij Rudnicki
      One more case, where BIA is not used by OLAP, that we just discovered:
      4) In 3.x queries, that still have CKFs with “Calculate before Aggregation” property on.

      Cheers,
      -Vitaliy

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