DMO: introducing the benchmarking tool

Posted 2020-12-23 weikui

This blog introduces the benchmarking tool for checking the migration rate prior to database migration option (DMO). As a prerequisite, you should read the introductionary document about DMO: Database Migration Option (DMO) of SUM – Introduction

 

Tuning the DMO procedure to shorten the downtime is an important task. With Software Update Manager (SUM) 1.0 SP13, we have an additional, important feature, to be added as the very first technique in the list of means to reduce the technical downtime:

 

How to tune DMO downtime

1. Before the DMO run: use the benchmarking tool to evaluate the migration rate for an existing system
2. Before the DMO run: consider to run SUM/DMO on an Additional Application Server (AAS, fka DI) instead of PAS
3. During the DMO test run: adapt the number of R3load processes to balance the performance of the SAP application server
4. After a (successful) test run: provide the “table duration files” for the next DMO run to optimize the table split mechanism
5. If downtime expectations are not met, consider using “downtime optimized DMO”, see
   DMO: downtime optimization by migrating app tables during uptime (preview)

 

Scope of benchmarking tool

 

• The benchmarking tool offers a fast check for possible migration speed prior to the DMO run
• The source system may continue to run (uptime)
• You can select specific tables, or use a specific percentage of all tables for the benchmarking run
• You can benchmark the export from the source system only, or benchmark the export and the import to the SAP HANA DB

 

What is the benchmarking tool

 

• The benchmarking tool is – trara: the SAPup (as part of the Software Update Manager, SUM)
• SAPup is triggering R3load for the export and import, like during the DMO run
• Prerequisite is the download folder, containing the source and target kernel files, like for DMO
• SAPup will not create a shadow repository, and skip other phases as well,
  that is why the benchmarking run is so fast (and cannot be used for a real migration/system copy)

 

How to start the benchmarking tool

• Prerequisite is that no DMO run is active, that means:
  if you have started a DMO before, you will have to reset the DMO run, cleanup, and stop all SAPup processes
• You start the benchmarking tool as the “migtool” option of SUM/DMO with a slightly different URL:
  https://<host>:1129/lmsl/migtool/<SID>/doc/sluigui
• The SL UI will show dialogs to select the benchmarking options, and the number of R3load processes to be used
• After the benchmarking run, a dialog will prompt you to analyze the log file to check the migration rate
• It is not possible to use the benchmarking tool while using the “old DMO UI” (with URL suffix /doc/gui)

 

Things to keep in mind

• Tuning: you should adapt the number of R3load processes for optimized usage of the application server performance (like in DMO), and then analyze the log file to check the migration rate
• Naming: the R3loads for “UT” are used for the preparation (determine tables for export), the R3loads for “DT” are used for the export (and import, if selected), so UT and DT are no indication for uptime or downtime (concerning the configuration of R3load processes)
• You will have to fulfill the same requirements for the source database software release as for DMO. If you use a lower database software version, you may get cryptic error messages
• Uptime or downtime benchmarking: you may consider to shut down the SAP system to tune the optimum number of R3loads for the DMO downtime run
• Documentation: the benchmarking tool is described in the DMO guide, section “Migration Tools”
• Migtools: “Migration Tools” are a) the benchmarking tool, and b) the standalone table comparison option of SUM. The latter is used for classical migration, and described in the guide of the Software Provisioning Manager (SWPM)
• Benchmarking the export: if you select the option to only export selected data from the source database, SAPup will trigger the R3load with the option “discard”, which will not create any files. This allows you to analyze the speed of the export from the source database without creating files, as the DMO run will not create export files either
• Using the benchmarking tool to do a system copy is not supported by SAP
• [Added on August 29th] For an oracle database, you will have to provide the BRCONNECT tools in the download folder