  Rise of hundreds cores technologies bring again to the first plan the problem
of interprocess synchronization in database engines. Spinlocks are widely used
in contemporary DBMS to synchronize processes at microsecond timescale. Latches
are Oracle RDBMS specific spinlocks. The latch contention is common to observe
in contemporary high concurrency OLTP environments.
  In contrast to system spinlocks used in operating systems kernels, latches
work in user context. Such user level spinlocks are influenced by context
preemption and multitasking. Until recently there were no direct methods to
measure effectiveness of user spinlocks. This became possible with the
emergence of Solaris 10 Dynamic Tracing framework. DTrace allows tracing and
profiling both OS and user applications.
  This work investigates the possibilities to diagnose and tune Oracle latches.
It explores the contemporary latch realization and spinning-blocking
strategies, analyses corresponding statistic counters.
  A mathematical model developed to estimate analytically the effect of tuning
_SPIN_COUNT value.
