Schema is available, not that it is enabled. To enable it, you must do so at server startup, as described in the next section. 

## 27.3 Performance Schema Startup Configuration 

To use the MySQL Performance Schema, it must be enabled at server startup to enable event collection to occur. 

The Performance Schema is enabled by default. To enable or disable it explicitly, start the server with the performance_schema  variable set to an appropriate value. For example, use these lines in the server my.cnf  file: 

[mysqld] performance_schema=ON 

If the server is unable to allocate any internal buffer during Performance Schema initialization, the Performance Schema disables itself and sets performance_schema  to OFF , and the server runs without instrumentation. 

The Performance Schema also permits instrument and consumer configuration at server startup. 

To control an instrument at server startup, use an option of this form: 

--performance-schema-instrument=’ instrument_name = value ’ 

Here, instrument_name  is an instrument name such as wait/synch/mutex/sql/LOCK_open , and value  is one of these values: 

• OFF , FALSE , or 0 : Disable the instrument 

• ON , TRUE , or 1 : Enable and time the instrument 

• COUNTED : Enable and count (rather than time) the instrument 

Each --performance-schema-instrument  option can specify only one instrument name, but multiple instances of the option can be given to configure multiple instruments. In addition, patterns are permitted in instrument names to configure instruments that match the pattern. To configure all condition synchronization instruments as enabled and counted, use this option: 

--performance-schema-instrument=’wait/synch/cond/%=COUNTED’ 

To disable all instruments, use this option: 

--performance-schema-instrument=’%=OFF’ 

Exception: The memory/performance_schema/%  instruments are built in and cannot be disabled at startup. 

Longer instrument name strings take precedence over shorter pattern names, regardless of order. For information about specifying patterns to select instruments, see Section 27.4.9, “Naming Instruments or Consumers for Filtering Operations” . 

An unrecognized instrument name is ignored. It is possible that a plugin installed later may create the instrument, at which time the name is recognized and configured. 

To control a consumer at server startup, use an option of this form: 

