DMO: comparing pipe and file mode for R3load
- Both the heterogenous system copy of Software Provisioning Manager (SWPM) and DMO of SUM support the migration to SAP HANA Database
- Both SWPM and SUM trigger R3load for the export from the source DB and the import into the SAP HANA DB
- But DMO has both R3loads running on the same host: on the primary application server (PAS, fka central instance CI)
(see DMO: technical background)
The “classical migration” (heterogenous system copy of SWPM) uses either the file mode or the socket mode.
Using the file mode, the data are exported, and written into a file, using compression. The file is transferred over the network:
Using the socket mode, the data are exported and transferred over the network:
Now with DMO, both R3load are running on the same host, and they communicate using the main memory of that host, using the pipe mode per default:
❗ Warning (Unix only)!
Do not use the statement grep* on the migrate_* directories to check for error messages. This generic grep statement may corrupt the named pipes used in R3load communication and cause errors in R3load processing. (Using “grep*.LOG” in these directories is not dangerous.)
Even with DMO, it would be possible to switch to the file mode. The R3load exports the data into a temporary file of limited size. As soon as this file is processed and the data are imported into the target DB, the temporary file is deleted.
- Compression is used for creating the file
- For windows OS, the pipe mode is enabled starting with SUM SP13 (available since April 28th 2015)
- I have no scenario when you would want to switch from pipe to file mode.
Product Manager, Software Logistics, SAP SE
[Update on June 1st 2015] File mode for DMO does use compression (this was initially wrongly stated in the blog).
[Update on March 15th 2016] Removed graphic for DMO file mode and shortened text; added warning on grep statement.