Connection to a database

I have a script in which data from an ORACLE database are called. The problem is that the connection isn't always succesfull. After 3-4 attempts the connection is succesfull. Do you know why does ths happen? Thanks

[Andreas Goser]

It would help if you can provide how exactly your code looks like and the error messages if any.

[the cyclist]

Are you certain that it is not something outside of MATLAB that is failing? It would be unusual for the code itself to be a source of intermittent failure.

[Fragkiskos Nikolakis]

the query for the database is

function[Vessel_Data]=stpQuery(selected_fields1)

% Set preferences with setdbprefs.
s.DataReturnFormat = 'dataset';
s.ErrorHandling = 'store';
s.NullNumberRead = 'NaN';
s.NullNumberWrite = 'NaN';
s.NullStringRead = 'null';
s.NullStringWrite = 'null';
s.JDBCDataSourceFile = '';
s.UseRegistryForSources = 'yes';
s.TempDirForRegistryOutput =  'Path';
s.DefaultRowPreFetch = '10000';
setdbprefs(s)

% Make connection to database.  Note that the password has been omitted.
% Using ODBC driver.
conn = database('Base','usr','pswd');

% Read data from database.
e = exec(conn,selected_fields1);
e = fetch(e);
close(e)
% Assign data to output variable.
Vessel_Data = e.Data;
% Close database connection.
close(conn)

Answer 1

[Piyush Kumar]

@Fragkiskos Nikolakis,

The intermittent connection issue to a database may be due to several problems -

• Network issues: Check the network connectivity of the server where the database is hosted and the server from where you are trying to connect.
• Database load: If the database server is under heavy load, it might not be able to handle all connection requests immediately.
• Timeout settings: Check the connection timeout-related settings of the database.

Refer to the following resources to get more details -

• https://stackoverflow.com/questions/162255/how-to-check-the-maximum-number-of-allowed-connections-to-an-oracle-database
• https://dba.stackexchange.com/questions/218020/how-do-i-check-the-connection-timeout-in-oracle
• https://www.databasestar.com/oracle-connection-issues/