Hello,
We have also performed the combination Unicode conversion + Oracle OLTP table compression.
Like already said before, after this operation you will end up with a reorganized database in Unicode with OLTP table compression active.
We reduced a 21 Tb database (non Unicode !) to 6,8 Tb (Unicode UTF-8 + OLTP table compression + reorganized).
We have also performed a test without compression, we went from 21 Tb then to 16 Tb.
We are now live for 3 months with OLTP talble compression and the overall DB performance is even better as before (much less disk reads as before).
We did NOT include Oracle index compression for the moment !
During your Unicode import you can select on which table spaces you want OLTP table compression.
Afterwards sapinst will make sure that during the Unicode import all tables are OLTP compressed (index compression is not included here, this is a totally different process).
The coming month we will have a look at Oracle index compression also.
This can be done by online rebuilding the indexes but there is a potential performance issue afterwards, so good testing is necessary.
During Unicode import sapinst also excludes some tables from compression (tables that are already compressed by SAP such as REPOLOAD, ARFCSDATA, EDI40, ...).
Note 1436352 - Oracle 11g Advanced Compression for SAP Systems
Note 1289494 - FAQ: Oracle compression
Also have a detailed look on Oracle licensing because some of the Advanced Oracle compressions require supplementary licensing.
Hope this was useful to you.
Regards.
Wim