Aligning storage costs with data value is a key element to incorporate into any in-memory database management strategy. This alignment, commonly referred to as the multi-temperature approach, has become increasingly prevalent as SAP HANA deployments and the cost associated with this database continue to grow. SAP's Near Line Storage (NLS) solution is designed to address these data management issues.

Multi-temperature approach :

The multi-temperature approach consists of storing the data in a database corresponding to its use and frequency of access. The main SAP HANA database, defined as "HOT", guarantees an optimal level of performance with frequent read and write access. In the example below, the SAP IQ database, defined as "WARM", is used as the target database for Near Line Storage. It behaves like a slave database that can be disconnected at any time without impacting the BW system. This database allows you to continue reporting on your data with degraded performance. The data is nevertheless frozen and it is not possible to write new data. Cold data, or "COLD", is used for data that must be kept but does not need to be consulted, generally for legal and regulatory reasons.

SAP-Bilink-nls-hana business intelligence tools and solutions

Source: www.sap.com

The main benefits of deploying the NLS solution are

  • Keep control of infrastructure ownership and operating costs (reduction and stabilisation of the size of the SAP Hana database),
  • Gain stability and agility (faster system copy, faster backup restore, reduction in size of non-productive systems)
  • Maintain a good level of performance on frequently used data,
  • Maintain instant access to archived data via NLS while maintaining your reporting tools

Main limitations of the tool :

Depending on the different versions of BW, there are several limitations of the tool to consider before opting for a Near Line Storage solution:

  • It is not possible to load data onto an archived data set. (It is planned that exceptional loading of data will be made possible in the BW 7.5 next feature PACK). ) However, some SAP partners, such as Datavard's Outboard solution, make it possible to load data onto an archived set by installing specific programs.
  • The performance of queries targeting archived data is degraded. This performance degradation can be significant, especially if you are in 7.3 without the possibility of using smart data access (SDA). In this case, strong performance degradation is to be expected if you have variables on navigation attributes and/or on hierarchies.
  • Only certain structural changes are allowed once the data has been archived. However, it is always possible to reload the data from your NLS target database to the HANA database in order to make unsupported changes.
  • Archiving by year is not possible for WO DSOs. Only archiving by request is possible. This can cause problems as it is common to have several years in a single request (e.g. Initialization). Special attention must be paid to this type of object.
  • The standard DSO must have a time characteristic in keys in order to be archived without constraints. It is possible to archive if the time dimension is not in keys. This strategy can be risky and requires special analysis as the data is not automatically locked by the system.
  • The abap routines that need to read data from the NLS target database need to be adapted.

In conclusion, NLS is a tool that is highly integrated with the BW platform and easy to use. This archiving solution, despite some limitations, allows you to archive data while remaining transparent to your users. An NLS project can be extremely quick to complete depending on the version and complexity of the BW landscape. It is strongly recommended to proceed step by step without planning a massive archiving of your data. The first and most crucial step in any NLS project will be to analyse the use and loading of your data in order to select the right "candidates " for your archiving. The definition of a good data aging strategy is the key to the success of your Near Line Storage project.

Useful links :

NLS Overview Page in SCN: http://scn.sap.com/docs/DOC-54468

Central Note: Note 1796393 -SAP BW near-line solution with Sybase IQ First Guidance: http://scn.sap.com/docs/DOC-39627

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Geoffroy Barrois

With 15 years of experience acquired during major transformation projects and an engineering background, Geoffroy works with our clients as a solutions expert on the SAP business intelligence suite. He is able to conduct a precise analysis of the needs and challenges faced by reporting managers, delivery managers and business owners of international groups. His functional and technical knowledge, his project management skills and his interpersonal skills enable him to work on a wide range of missions
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