We are on 12.2.1.4 oracle forms and reports 12c on windows 2016. We have standalone report server queues defined which runs the reports fine but when we submit large report generating more than 300 pages, report services slows down, the slow down is observed in page formatting, the number of pages being formatted per sec gradually slows down. Same report is 3 times faster on 10g forms and reports for eg 15 mins vs 5 mins.
Database is not a bottleneck, as we have checked the query in the database finishes off in 8-10 secs.
Trace:32 on reports shows the slowness in pages being formatted but what is causing the slowness is not known. CPU is at 25 % (4 vcpus).
The VMs are hosted on OCI.
How can we find the root cause, as to why the page formatting performance degrades as the page increases?