The variable value. 

The user_variables_by_thread  table has these indexes: 

•Primary key on ( THREAD_ID , VARIABLE_NAME ) 

TRUNCATE TABLE  is not permitted for the user_variables_by_thread  table. 

## 27.12.11 Performance Schema Replication Tables 

The Performance Schema provides tables that expose replication information. This is similar to the information available from the SHOW REPLICA | SLAVE STATUS  statement, but representation in table form is more accessible and has usability benefits: 

• SHOW REPLICA | SLAVE STATUS  output is useful for visual inspection, but not so much for programmatic use. By contrast, using the Performance Schema tables, information about replica status can be searched using general SELECT  queries, including complex WHERE  conditions, joins, and so forth. 

•Query results can be saved in tables for further analysis, or assigned to variables and thus used in stored procedures. 

•The replication tables provide better diagnostic information. For multithreaded replica operation, SHOW REPLICA | SLAVE STATUS  reports all coordinator and worker thread errors using the Last_SQL_Errno  and Last_SQL_Error  fields, so only the most recent of those errors is visible and information can be lost. The replication tables store errors on a per-thread basis without loss of information. 

•The last seen transaction is visible in the replication tables on a per-worker basis. This is information not avilable from SHOW REPLICA | SLAVE STATUS . 

•Developers familiar with the Performance Schema interface can extend the replication tables to provide additional information by adding rows to the tables. 

## Replication Table Descriptions 

The Performance Schema provides the following replication-related tables: 

•Tables that contain information about the connection of the replica to the source: 

• replication_connection_configuration : Configuration parameters for connecting to the source 

• replication_connection_status : Current status of the connection to the source 

• replication_asynchronous_connection_failover : Source lists for the asynchronous connection failover mechanism 

•Tables that contain general (not thread-specific) information about the transaction applier: 

• replication_applier_configuration : Configuration parameters for the transaction applier on the replica. 

• replication_applier_status : Current status of the transaction applier on the replica. 

•Tables that contain information about specific threads responsible for applying transactions received from the source: 

