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Near-Line Storage With Straggler Management

Near-Line Storage (NLS) is one of the many features of SAP BW for DATA Archiving. With the help of NLS solution the “cold” data is offloaded from HANA DB to Sybase IQ which acts as a secondary database.

Stages in which data archiving takes place

Technical PhasesFunctionality
Copy Phase
The data from HANA system gets copied to Sybase system based on data requests. The commit ID gets generated for all the data requests and the last commit ID is used to verify the data accuracy.
Verification phase The verification of the copy phase is performed based on the commit ID’s retrieved. This is to ensure that the data copying has been completed.
Deletion PhaseUpon successful completion of verification phase, the data from HANA get deleted by storing the last retrieved commit ID of copy phase (this is done in order to get the data back from Sybase when required).

Data Locking without & with Straggler Management

How does Straggler Management Work?

  • During Data Store Object Activation, data records violating already-archived time slices will be handled via Straggler Management.
  • Records violating the archiving condition will be updated via separate “Delta Request” whilst allowing for the rest of data-load to complete.
  • Updates to subsequent data targets will still contain the violated records data, hence complete delta information is received.

How does it differ from Error Stack?

  • With Error Stack, records with archiving lock violation are kept in error stack.
  • The locked time-slice must be restored from NLS to HANA first before data re-loading from Error Stack.
  • The same time-slice will then have to be re-archived to stabilize HANA capacity.

Configuring Straggler Management

Straggler management can be configured in the following way as depicted in the screenshots below:

At Data Archiving Process (DAP) Creation level

After activation of the DAP (Data Archiving Process), it will enable the processing of Straggler Management. This means that the Data Store object activation process can detect and handle exceptions.

At DSO Request Activation level
At Process Chain Configuration level

Conclusion

The Straggler Management is crucial to fix the data archiving issues that SAP customers faces during archiving. Inclusion of straggler management gives customer a provision to archive the data to Sybase without worrying on the age-old issue of data locking.

Suggested links

NLS Solution

https://blogs.sap.com/2016/10/12/sap-nls-solution-sap-bw/

Understand NLS Archiving

https://www.scribd.com/document/353248380/SAP-BW-Near-Line-Storage-NLS-Implementation-for-Sybase-IQ

Enable Straggler Management

https://apps.support.sap.com/sap/support/knowledge/preview/en/2573961

Contact for further details:

Syed Sajjad
Technical Team Lead – Analytics
sajjads.in@mouritech.com
MOURI Tech

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