question: @ Override public void start ( Xid xid , int flags ) throws XAException { if ( isDebugEnabled ( ) ) { debugCode ( "start(" + JdbcXid . toString ( xid ) + ", " + quoteFlags ( flags ) + ");" ) ; } if ( flags == TMRESUME ) { return ; } if ( flags == TMJOIN ) { if ( currentTransaction != null && ! currentTransaction . equals ( xid ) ) { throw new XAException ( XAException . XAER_RMERR ) ; } } else if ( currentTransaction != null ) { throw new XAException ( XAException . XAER_NOTA ) ; } try { physicalConn . setAutoCommit ( false ) ; } catch ( SQLException e ) { throw convertException ( e ) ; } currentTransaction = xid ; prepared = false ; }
target:  Start or continue to work on a transaction.