If you get the following message, check the firewall settings.

ERROR 30-09 09:13:36,485 - YOUR_LOG_CONNECTION - Error disconnecting from database:
Error comitting connection
 Io exception: Socket read timed out

When the transformation/job is started, Kettle opens a connection for logging. The transformation could run for hours, the connection for logging will stay idle all this time and it might be dropped by the firewall. When the transformation finishes execution, stopped by the user or fails with an error and Kettle tries to update the log, it notices that the connection is dropped and displays the error messages.

The other messages appearing in the log:

ERROR 30-09 09:13:36,485 - CONNECTION - org.pentaho.di.core.exception.KettleDatabaseException:
 Error comitting connection
 Io exception: Socket read timed out

 at org.pentaho.di.core.database.Database.commit(Database.java:635)
 at org.pentaho.di.core.database.Database.commit(Database.java:605)
 at org.pentaho.di.core.database.Database.disconnect(Database.java:496)
 at org.pentaho.di.trans.steps.databaselookup.DatabaseLookup.dispose(DatabaseLookup.java:662)
 at org.pentaho.di.trans.step.BaseStep.runStepThread(BaseStep.java:2918)
 at org.pentaho.di.trans.steps.databaselookup.DatabaseLookup.run(DatabaseLookup.java:672)
 Caused by: java.sql.SQLException: Io exception: Socket read timed out
 at oracle.jdbc.driver.DatabaseError.throwSqlException(DatabaseError.java:112)
 at oracle.jdbc.driver.DatabaseError.throwSqlException(DatabaseError.java:146)
 at oracle.jdbc.driver.DatabaseError.throwSqlException(DatabaseError.java:255)
 at oracle.jdbc.driver.T4CConnection.doCommit(T4CConnection.java:533)
 at oracle.jdbc.driver.PhysicalConnection.commit(PhysicalConnection.java:1128)
 at org.apache.commons.dbcp.DelegatingConnection.commit(DelegatingConnection.java:238)
 at org.apache.commons.dbcp.PoolingDriver$PoolGuardConnectionWrapper.commit(PoolingDriver.java:259)
 at org.pentaho.di.core.database.Database.commit(Database.java:625)
... 5 more

ERROR 30-09 09:13:57,014 - TRANSFORMATION - org.pentaho.di.core.exception.KettleException:
 Error writing log record to table [{0}]ETL_LOG]

Couldn't execute SQL: UPDATE ETL_LOG SET STATUS=? , LINES_READ=? , LINES_WRITTEN=? , 
 LINES_UPDATED=? , LINES_INPUT=? , LINES_OUTPUT=? , ERRORS=? , STARTDATE=? , ENDDATE=? , 
 LOGDATE=? , DEPDATE=? , REPLAYDATE=? , LOG_FIELD=? WHERE ID_BATCH=?

ERROR 30-09 09:14:34,981 - JOB - A serious error occured : 
org.pentaho.di.core.exception.KettleJobException: 
Unable to end processing by writing log record to table JOB_LOG

Couldn't execute SQL: UPDATE JOB_LOG SET STATUS=? , LINES_READ=? , LINES_WRITTEN=? ,
 LINES_UPDATED=? , LINES_INPUT=? , LINES_OUTPUT=? , ERRORS=? , STARTDATE=? , ENDDATE=? ,
 LOGDATE=? , DEPDATE=? , REPLAYDATE=? , LOG_FIELD=? WHERE ID_JOB=? 

Io exception: Connection reset by peer: socket write error