Monday, January 2, 2017

BW: Conversion of DB tables to from Row Store to Column Store

Within a move of SAP NetWeaver based system from any DB to HANA DB there are many steps involved. Also a step of converting tables from row to column based is one of them.

Running the system on HANA DB you can have the table regardless of it store type (either row store or column store). Then depending on type of the system (OLTP or OLAP) majority of tables are set to one of the store types. E.g. in case of OLAP system (e.g. SAP BW) most of the tables are type of column store tables because it delivers a better performance in case of data warehouse data processing (running queries, transforming the data, etc). Also it delivers better compression rate in case of OLAP. On other side in the systems like OLTP it requires balanced approach whereas for some table a row store might be better and for others column store concept.

During HANA migration (or even before that to minimize downtime) an ABAP report called RSDU_MOVE_TO_COLUMN is used convert the tables based on row store to column store. However the program can be run even after the migration to find out what are tables that have potential to be converted to column store. The report has several modes of runtime. In the “Check only” mode a list of biggest row store tables is provided.

Also to see to what store type a particular table is set; see table DD09L (DD: Technical settings of tables) and its field (ROWORCOLST - For distinction between Row or Column Store) in particular.

More information:

2044047 - Pre-BW7.4 SP08 RowStore-to-ColumnStore conversion

No comments: