As we all know Exadata Storage indexes use to hold information up to eight columns till Exadata Storage Server Software release 126.96.36.199 , now with the of Oracle Exadata Storage Server Software release 188.8.131.52.0, storage indexes have been enhanced to store column information for up to 24 columns.
It is important to understand that only space to store column information for eight columns is guaranteed. For more than eight columns, space is shared between column set membership summary and column minimum/maximum summary. The type of workload determines whether set membership summary gets stored in storage index. I am hopping to test out this new feature shortly and will post results for my readers.