When I first tried to do a test migration from a Windows 2008 R2 x64/SQL Server 2008 R2 x64 System to Windows 2008 R2/Sybase ASE 15.7 x64 for our RDS Qualification, I wrote the blog My first Sybase ASE migration experience.
At that time, this experience did lots of cofusions on my side and on community side.
Some partners and customers in Turkey asked me if the data growth is real when you migrate from SQL Server to Sybase ASE.
The answer is important, because there are 5 customers (2 are Holding, means lots of systems and sub-companies) who are waiting to migrate to Sybase ASE.
That's why, as a SAP Partner, we discussed this issue with SAP Team. jan.stallkamp helped me to clarify cloudy parts of this issue.
Yesterday I did my second migration from a 350G database of same source into Sybase ASE to see a more realistic result.
Migration Landscape
Source System | Target System | |
OS Version | Windows 2008 R2 SP1 x64 | Windows 2008 R2 SP1 x64 |
DB Version | SQL Server 2008 R2 (10.50.1702) x64 | Sybase ASE 15.7.0.021 x64 |
SAP Solution | SAP ERP 6.0 EHP5 | SAP ERP 6.0 EHP5 |
SP Level | SAPKB70209, SAPKA70209 | SAPKB70209, SAPKA70209 |
CPU | 4 VCPU (2.8GHz) | 4 VCPU (2.8GHz) |
RAM | 36 GB | 36 GB |
DB Size | 338,4 GB | 346,5 GB (2,39% growth) |
Here are the DB02 information for both Source and Target DBs.
| Source System | Target System |
|---|---|
 |
|
The result is a bit different than the previous migration as you can see.
So, lets talk about what is actually changed and made this difference.
Whas has changed?
1. DB size for Source System
We did the first migration with a quite small SQL DB with 54 GB in size. As you can imagine, this is a very emtpy system DB size and will never reflect a customer system.
So, this time I tried to do the migration with a ~ 350 GB system. For this, I copied an existing system client into several clients (10 actually :smile: )
So, now we can say that it is nearly a customer system (test or development may be ha?)
2. New Installation Media
After discussing the issues in first migration with Jan, we noticed that there are issues with SAP Standart Tables using LOBs.
Sybase ASE can store LOBs either on the normal data pages (on-row) or on separate pages (off-row). The threshold we have implemented to switch between this two ways to store data was set by SAPInst to 2000 for your system. Unfortunately the mentioned tables contain a lot of LOBs that are larger than this threshold but not ‘really large’. This results in bad space consumption.
SAP changed the SAP installer to have better settings for this kind of tables also put this feature into Sybase ASE with ESD#02.
To get advantage of in-row-LOB compression you will need to have 15.7.0.021 in place before the load starts (or do reorgs after the system is migrated).
See SAP Note 1773862 about 15.7.0.021
Another Issue was about the empty tables. As my system was quite small the overall size is significantly impacted by the size of empty tables. There are a lot of database tables in an SAP system that are not used for your type of operations. But creating an empty table on disk costs some amount of space.
Therefore ASE development put a feature (and this is delivered with 15.7 ESD#2) to not create empty on disk but only store them in the system catalogs. Creating a table will happen as soon as the first write operation happens.
Used Installation Medias
3. Interpretation of DB02 (or DBACOCKPIT) for Sybase ASE
This is the easiest part. Because it is possible to misunderstand the DB02 values if you're not familiar with ASE (As I was).
In the first screen of DBACOCKPIT, under Space > Databases, the Database Size (MB) is showing the full size of Datafiles (whether allocated or not) plus the Log space.
In my system, this value is 419.840 MB (419,8 GB).
First you've to remove the log space size. You can see the log device and data device sizes in the same screen.
Here remove 10 GB from 419 GB.
You also have to remove the unused space which is 63 GB.
So, resulting size is 346,5 GB which is almost same as SQL Server.
Result
Sybase ASE provides the same data compression as Microsoft SQL Server 2008 R2.
So, migrating from any other database to Sybase ASE will give you the same reduced DB Size as SQL Server.
I want to thank jan.stallkamp again for his support during this tests.
- SAP Managed Tags:
4 Comments
