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Process Overview

Data from one request is stored with its own request identity in the F table. This has the advantage that you can easily check and delete single requests. But in general identical data (with the same combination of DIMs except Package Dimension) is stored multiple times in the F fact table. Hence, the data volume may increase more than necessary with time.

TASK of CONDENSOR

Data records of requests are aggregated and stored in the E-fact table with the requestID=0. Hence the compressed data is stored in the E-table, the uncompressed requests are stored in the F-table. Compression has in general the following advantages:

  • less amount of data in the fact tables
  • in case ORACLE is used this also means that we have less partitions in the fact table (see Note 590370)
  • shorter query runtime
  • if the data is stored in the E table, you can also improve the query performance with the help of the feature 'partitioning'

PROCESS STEPS

In case you compress more than one request the system handles one after the other (in a row) and carries out an 'commit' in between. As a consequence the condensor doesn't have to carry out a rollback for all requests if the process terminates. Roughly we have the following processing steps/logic:

  • Loop over ReqestIDs
    • Update/Insert of E fact table
    • Delete corresponding entry of package dimension (logical deletion)
    • Commit
  • End Loop
  • Delete (Drop) requests of fact table (physical deletion)
  • Compress Aggregates (if exist)

Please see note 407260 for further details.

Topics/Features

SAP Support Troubleshooting Guideline  

 SSG BW-BEX-OT-DBIF-CON

SAP Online Documentation

Compressing InfoCubes

SAP Consulting Notes

List of notes/KBAs:

  • 1928103     BW on SAP HANA: Performance of InfoCube compression
  • 1811659     SAP HANA InfoCube: Cleaning up duplicates in compressed data
  • 1780575     HANA: Konvertierung scheitert mit Fehler "RSDRI_HDB 059"            
  • 1773398     SAP HANA: No compression for scale-out & non-optimized cube
  • 407260       FAQs: Compression of InfoCubes
  • 590370      Too many uncompressed request (f table partitions)
  • 1778638    Important Facts concerning the compression of InfoCubes
  • 2121399    Cannot compress InfoCube requests
  • 2412837    InfoCube compression does not work (NOP key figures)
  • 2521338    Compression with Zero Elimination does not work
  • 1669300    Parallelism during BW cube compression on Oracle
  • 1795551    Compression Error 'Multiple markers have the same key'
  • 1472386    'ORA-04031 out of memory error in BW systems'.
  • 430486      Overview/repair of F fact table of an BW InfoCube
  • 1012829    DB6: Long Running BW Compression
  • 1587759    Duplicate Records in InfoCube Dimensions
  • 869407      Partitioning on Microsoft SQL Server
  • 2864705 Report SAP_FIND_EFACT_DUPLICATES
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