It is generic and only dated to the extent that there is more information now. The concepts and methods are still sound and can be applied to today's systems.
Want to know about SAR?
When you time an application do you want to know what the user-state CPU time and systemstate CPU time means?
Many of the pertinent questions and answers to System Performance Tuning are in this book. The chapters are:
Introduction to System Performance
Monitoring System Activity
Managing the Workload
Memory Performance
Disk Performance Issues
Network Performance
Terminal Performance
Kernel Configuration
Appendix A Real-time Processes
Appendix B A Performance Tuning Strategy
This book has helped point to the pertinent manuals on several flavors of UNIX.