• LOCK_DURATION 

The lock duration from the metadata lock subsystem. The value is one of STATEMENT , TRANSACTION , or EXPLICIT . The STATEMENT  and TRANSACTION  values signify locks that are released implicitly at statement or transaction end, respectively. The EXPLICIT  value signifies locks that survive statement or transaction end and are released by explicit action, such as global locks acquired with FLUSH TABLES WITH READ LOCK . 

• LOCK_STATUS 

The lock status from the metadata lock subsystem. The value is one of PENDING , GRANTED , VICTIM , TIMEOUT , KILLED , PRE_ACQUIRE_NOTIFY , or POST_RELEASE_NOTIFY . The Performance Schema assigns these values as described previously. 

• SOURCE 

The name of the source file containing the instrumented code that produced the event and the line number in the file at which the instrumentation occurs. This enables you to check the source to determine exactly what code is involved. 

## 27.12.13.4 The table_handles Table 

• OWNER_THREAD_ID 

The thread requesting a metadata lock. 

• OWNER_EVENT_ID 

The event requesting a metadata lock. 

The metadata_locks  table has these indexes: 

•Primary key on ( OBJECT_INSTANCE_BEGIN ) 

•Index on ( OBJECT_TYPE , OBJECT_SCHEMA , OBJECT_NAME ) 

•Index on ( OWNER_THREAD_ID , OWNER_EVENT_ID ) 

TRUNCATE TABLE  is not permitted for the metadata_locks  table. 

The Performance Schema exposes table lock information through the table_handles  table to show the table locks currently in effect for each opened table handle. table_handles  reports what is recorded by the table lock instrumentation. This information shows which table handles the server has open, how they are locked, and by which sessions. 

The table_handles  table is read only and cannot be updated. It is autosized by default; to configure the table size, set the performance_schema_max_table_handles  system variable at server startup. 

Table lock instrumentation uses the wait/lock/table/sql/handler  instrument, which is enabled by default. 

To control table lock instrumentation state at server startup, use lines like these in your my.cnf  file: 

•Enable: 

[mysqld] performance-schema-instrument=’wait/lock/table/sql/handler=ON’ 

•Disable: 

