what are advantages of PPI?

Range queries don't have to utilize a Full Table Scan.

Deletions of entire partitions are lightning fast.

PPI provides an excellent solution instead of using secondary indexes

Tables that hold yearly information don't have to be split into 12 smaller tables to avoid Full Table Scans (FTS). This can make modeling and querying easier.

Fastload and Multiload work with PPI tables, but not with all Secondary Indexes