As you know We already on 18c version, but I still see some questions which are related performance issues and how We can use Statpack reports.

Its available since  Oracle 8i, I want to share some Metalink documents which covers what is Statspack report, How We can install&run and read it, Purpose of usage Statspack reports

Here are the related documents lists:

How to Identify Resource Intensive SQL for Tuning  Doc ID:232443.1
FAQ- Statspack Complete Reference  Doc ID:94224.1
TROUBLESHOOTING: Possible Causes of Poor SQL Performance    Doc ID:    33089.1

Installing and Configuring StatsPack Package [ID 149113.1]
FAQ- Statspack Complete Reference [ID 94224.1]
Creating a StatsPack performance report [ID 149124.1]
How To Understand AWR Report / Statspack Report [ID 842884.1]
What is StatsPack and where are the READMEs? [ID 149115.1]
Systemwide Tuning using STATSPACK Reports [ID 228913.1]
Oracle Applications and StatsPack [ID 153507.1]
How to Identify Resource Intensive SQL for Tuning  Doc ID:232443.1
TROUBLESHOOTING: Possible Causes of Poor SQL Performance Doc ID:33089.1