Source: FY community
show variables like 'max_connections'
max_connections: The maximum number of concurrent connections supported
The maximum permitted number of simultaneous client connections
show variables like 'innodb_thread_concurrency'
innodb_thread_concurrency: the maximum number of threads to support concurrent execution
InnoDB tries to keep the number of operating system threads concurrently inside InnoDB less than or equal to the limit given by this variable (InnoDB uses operating system threads to process user transactions). Once the number of threads reaches this limit, additional threads are placed into a wait state within a “First In, First Out” (FIFO) queue for execution. Threads waiting for locks are not counted in the number of concurrently executing threads.
thread_concurrency: the maximum number of threads to support concurrent execution
This variable is specific to Solaris 8 and earlier systems, it allows the application should prompt the number of threads running concurrently to the thread system. MySQL 5.7.2 To remove this variable.
This variable is specific to Solaris 8 and earlier systems, for which mysqld invokes the thr_setconcurrency() function with the variable value. This function enables applications to give the threads system a hint about the desired number of threads that should be run at the same time. Current Solaris versions document this as having no effect.This variable was removed in MySQL 5.7.2.
Views connection to the server
show status like 'Connections';
View once the maximum number of connections
show status like 'Max_used_connections';
View the number of threads that are currently connected
show status like 'Threads_connected';
View the number of threads that are currently running
show status like 'threads_running';
View the number of threads in the thread cache
show status like 'threads_cached';