In some cases, SUM will create the shadow repository on the target database in the future.
This blog provides background information as well as the current status of this new approach.
Introducing the shadow system and shadow repository
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 alredy 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 yet cover the aspects discussed below.
Until now, SUM creates 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 will change for a system conversion to SAP S/4HANA 1909 with SUM 2.0 SP 06 (general availability planned for mid of September 2019): SUM will create 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 is the first that 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.
No changes for SUM handling
(There is a new dialog sequence introduced with SUM 2.0 SP 06 – described in an upcoming separate blog – but this is not related to the shadow system.)
Advantages for conversions to S/4HANA 1909
That was the easy part – now to the fine-print part of the story …
Additional aspects of the story
- 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 will use the shadow repository on the target database only for a conversion to SAP S/4HANA 1909.
- The same SUM 2.0 SP 06 version, used for a conversion to SAP S/4HANA 1809 (or lower), uses the traditional approach with shadow repository on source database
(The same applies for the use of SUM 2.0 SP 06 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).
- We are evaluating the possibility for future SUM 2.0 SP versions to allow this approach also for targeting lower SAP S/4HANA versions, but can’t provide any guaranty.
- Restrictions: For a system conversion target SAP S/4HANA 1909 (which must use SP 06 or higher) the following scenarios are not supported with SUM 2.0 SP 06:
- DMO with system move (see blog https://blogs.sap.com/2017/05/22/dmo-with-system-move-the-use-case-to-change-pas-host-during-dmo/)
- Uptime Migration, aka downtime-optimized DMO (see blog https://blogs.sap.com/2014/09/08/dmo-downtime-optimization-by-migrating-app-tables-during-uptime-preview/)
- downtime-optimized Conversion for source on non-HANA database
(see blog https://blogs.sap.com/2019/03/08/system-conversion-to-sap-s4hana-downtime-optimized-conversion/ and SAP Note 2293733)
These scenarios are planned to be supported in later SP versions of SUM 2.0.
Product Manager SUM