HANA NSE how about delta merge for page loadable tables

[lgh0209]

Hello,

I want to know know how to handle the delta merge for page loadable tables with NSE enabled.

Thanks.

[lbreddemann]

What specifically do you want to know?

The delta merge operation is fully automatic in most cases with no need for "handling".

[andreas_baldauf]

I also want to understand how the delta merge process works if NSE is activated.

SAP note 2057046 “FAQ: SAP HANA Delta Merges” contains a description of the delta merge process for a partition without NSE. The records of Main1 and Delta1 are merged into the new Main2 (all storage containers are in the memory): Main1 + Delta1 => Main2

The question is how does the delta merge process works If NSE is activated for a table / partition (load unit: page loadable). If NSE activated, the records of the partition are stored on disk (Disk1), in the buffer (Buffer1) and in the delta area (Delta1). According to my understanding, the delta merge process has to read the records of Disk1, Buffer1 (optional) and Delta1 to be able to create the new storage container which contains all relevant records (Disk2): Disk1 + Buffer1 (optional) + Delta1 => Disk2

If my assumption is correct, I expect that constantly reading data from and writing data to the disk will have a negative impact on the performance of the system.

[hemanth_nirmal_kondeti]

That could be true i guess.

we have activated NSE for our ETD system for couple of tables. Once we done that we have problems on our head.

Delta merge for table size 7M records takes 20-30 mins as a result entire application is behaving mad.