on 01-15-2016 3:57 PM
Hi folks,
It is my understanding that when replicating SAP tables from SAP Oracle db to HANA sidecar db we are able to store tables in HANA using much less physical disk space due to compression.
Now in contrast we are taking one of our SAP Oracle db's and converting to SAP directly on HANA (No sidecar db and no replication involved). Some of the consultants are saying in this case the tables that were in Oracle will now take up to 3 times more disk space on the SAP on HANA db. Can somebody confirm if this is true?
Thanks,
-Patrick
PS: I wonder if they are mistaken and thinking of memory consumption and delta merge process.
Hi Patrick.
The migration from Oracle to SAP HANA will not decrease the size of the DB only by using compression. All the data structure in SAP HANA is different from any other DB and is very space optimized, so this wil also have an impact on the final size of the DB.
"Now in contrast we are taking one of our SAP Oracle db's and converting to SAP directly on HANA"
What kind of task are you doing? Heterogeneous Copy using SWPM or Data Migration using DMO?
There are several SAP notes that can give you a script to run and get the needed memory size for your landscape.
Regarding the 3X times de space, I think that they are talking about the SAP HANA metrics for sizing the persitence (disk space). The new docs say 4X times the memory...
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Ok I was told they are using neither Heterogenerous or DMO but rather importing data based upon custom programs or LSMW's. Also it looks like they were indeed mistaken and were thinking about memory. I'm sure they heard the standard story about how up to three times memory is needed to perform delta merge operations. That's my guess. But thanks for your help guys!
-Patrick
Hello Martin,
thanks for the really interesting before/after figures. Can you please let us know, if you used any kind of compression on the Oracle side before the migration?
Thank you,
Andreas
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I recently had the chance to compare the before / after situation of an Oracle -> SAP HANA migration in all aspects using the SQL statements from SAP Note 1438410 and 1969700. Here are two disk space related metrics:
- Database disk size (allocated):
Oracle: 16874 GB
SAP HANA: 3059 GB
- Database disk size (used):
Oracle: 15786 GB
SAP HANA: 2390 GB
Of course this is just one specific example and in other systems the ratio can be different.
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