Thanks frederico_fonseca and Jeff Moden for the extensive feedback.
I'm transfering 160 million rows of oracle 11g number (19,0) not null to sql server numeric(19,0) not null
Using SQL 2017 Enterprise + SSIS 2017
Original Dataflow: Oracle OLEDB Source -> SQL Server OLEDB Destination. No transformations. Fast Load Insert using variable
"Select mynumber from mytable" . Variable tablename "SQLServerMyTable"
"SQLServerMyTable" is a heap (no clustered index)
FastLoad : Keep Identity, Keep Nulls, Table Lock. Rows per batch 50000, Commit after 50000
Using OracleOLEDB it slowly grinded to a halt after 90 million records. Throughput started around 20 Mbps and every few minutes it would lower to 19 MBps, 18 Mbps, .... I was lucky to transfer 3 million records in a day. At the same moment average oracle "SQL*Net message from client" wait rose from 2 ms to 3 ms, 4 ms, ... 200 ms
Preliminary testing with ado.net doesn't grind to a halt (apperantly uses OCI). Will convert to Attunity when SQL Server 2019 is supported by our company backup software.
Free RAM on server : 28 GB. Going to keep an eye on it.