Lock Wait Timeout Issue ?

Why below mentioned error is coming ?

2018-08-27 10:01:00  WARN: Lock wait timeout exceeded; try restarting transaction - MySQLTransactionRollbackException (... < QueryBuilder:475 < DataManager:223 < DeviceManager:222 < ...)
2018-08-27 10:01:00  WARN: Lock wait timeout exceeded; try restarting transaction - MySQLTransactionRollbackException (... < QueryBuilder:475 < DataManager:223 < DeviceManager:222 < ...)
2018-08-27 10:01:00  WARN: Lock wait timeout exceeded; try restarting transaction - MySQLTransactionRollbackException (... < QueryBuilder:475 < DataManager:223 < DeviceManager:222 < ...)
2018-08-27 10:01:00  WARN: Lock wait timeout exceeded; try restarting transaction - MySQLTransactionRollbackException (... < QueryBuilder:475 < DataManager:223 < DeviceManager:222 < ...)
2018-08-27 10:01:51  WARN: Lock wait timeout exceeded; try restarting transaction - MySQLTransactionRollbackException (... < QueryBuilder:475 < DataManager:223 < DeviceManager:222 < ...)
2018-08-27 10:01:51  WARN: Lock wait timeout exceeded; try restarting transaction - MySQLTransactionRollbackException (... < QueryBuilder:475 < DataManager:223 < DeviceManager:222 < ...)
2018-08-27 10:01:51  WARN: Lock wait timeout exceeded; try restarting transaction - MySQLTransactionRollbackException (... < QueryBuilder:475 < DataManager:223 < DeviceManager:222 < ...)
2018-08-27 10:01:51  WARN: Lock wait timeout exceeded; try restarting transaction - MySQLTransactionRollbackException (... < QueryBuilder:475 < DataManager:223 < DeviceManager:222 < ...)

Looks like some tables got locked in your database.