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Boris_Rubarth
Product and Topic Expert
Product and Topic Expert
19,144

Abstract:





SUM creates the shadow repository on the target database for all migration scenarios.
This blog provides background information as well as the current status of this new approach.

Latest News [added on June 10th 2020]


With SUM 2.0 SP 08, the approach "shadow-repository-on-target-database" is used for all migration scenarios, independent on the target release (and independent on target database type). This blog was updated accordingly



Introducing the shadow system and shadow repository


The Software Update Manager (SUM) has several means to reduce the downtime of maintenance events like update/upgrade, database migration, or system conversion. One of these means is the shadow system.
A shadow system basically consists of a shadow instance and a shadow repository:


  • The shadow instance is an additional ABAP instance which is created by SUM on the application server on which the SUM was started. It is used to prepare steps executed during the downtime.

  • The shadow repository exists on target product version level. This means that the shadow instance must use the target kernel to create the shadow repository with potentially new object types.




The shadow system is already created and exists during uptime processing of SUM. As a consequence, the downtime is reduced.

[i] You can check this blog for an introduction to the shadow system, but this description does not cover the migration case.


Until SUM 2.0 SP 07, SUM created the shadow repository on the source database specifically for the migration scenarios Database Migration Option (DMO), and System Conversion to SAP S/4HANA for source systems with no SAP HANA database. (Note that non-migration scenarios have only one database, so that is no differentiation of source and target database is needed.)




This has changed for a system conversion to SAP S/4HANA 1909 with SUM 2.0 SP 06 (and higher): SUM creates the shadow repository on the target database. (Again: This only applies if the source system is not yet on SAP HANA database and a database migration happens. Only then we have a source and a target database).




 




The figure illustrates:

  • SHD REP: the shadow repository

  • PAS: the primary application server

  • PRD REP: the current (productive) repository of the source system




SAP S/4HANA 1909 and the ABAP kernel




SAP S/4HANA 1909 uses SAP kernel 7.77. This kernel version works exclusively with SAP HANA as database. As the shadow instance must use the target kernel, it is obvious that the shadow instance for SAP S/4HANA 1909 can't work with a database other than SAP HANA DB. That is the reason why SUM has to create the shadow repository on the target database for a migration scenario targeting SAP S/4HANA 1909.

Note: SAP Kernel 7.73 as well only supports SAP HANA as database, but it can be used for the shadow repository on source db in the conversion process targeting SAP S/4HANA 1809.




No changes for SUM handling


If you have used SUM 2.0 for a system conversion before, you will not experience any difference in the dialogs concerning the shadow system handling with SUM 2.0 SP 06. So, there is no user choice or parameter on the shadow system creation - SUM will simply do what is required.



(There is a new dialog sequence introduced with SUM 2.0 SP 06 - described in this blog - but this is not related to the shadow system.)



Advantages for conversions to S/4HANA 1909


The shadow repository created on the source system was the reason for some migration requirements concerning the source database. As an example, Oracle 11.2 database on source systems had to be upgraded to version 12 prior to the conversion run (or NZDT had to be used). And in some cases, it was required to extend the tablespace of the source database to create shadow repository. These requirements are now obsolete, when the shadow repository is no longer created on the source database. Good news!


Additional aspects of the story


SUM 2.0 SP 06 is the first SP version of the tool that uses the shadow repository on the target database - but not for all possible cases. Let me clarify some aspects and typical questions:


  • The requirement for a system conversion to have the source system on Unicode remains!

    • This was announced long ago (see announcement), so SUM 2.0 does not cover the Unicode conversion, and will neither in the future.



  • The conversion planning in Maintenance Planner still requires selecting both new kernels, for source and for target database.

  • SUM 2.0 SP 06 and SP 07 use the shadow repository on the target database only for a conversion to SAP S/4HANA 1909.

  • SUM 2.0 SP 08 and higher uses the same approach now for all migration scenarios
    (also for the use of SUM 2.0 SP 08 inside the classical SAP Business Suite, e.g. for the migration of SAP ECC 6.0 from a non-HANA database to EHP 8 on SAP HANA DB).




Boris Rubarth
Product Manager SUM



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