COPY DATABASE <name> TO <name> [ IF [ NOT ] EXISTS ]This command is used to copy an existing database to a new database. By default an error will be returned if the target database already exists. Specifying the optional IF NOT EXISTS keywords no error will be returned if the target database already exists. If the optional IF EXISTS keywords are specified and the target database already exists, then it will be removed before the copy. Both the databases must be closed before they can be copied.
In this article Barry Mavin, CEO and Chief Software Architect for Recital, details on how to use the Client Drivers provided with the Recital Database Server to work with local or remote server-side JDBC data sources.
Overview
The Recital Universal .NET Data Provider provides connectivity to the Recital Database Server running on any supported platform (Windows, Linux, Unix, OpenVMS) using the RecitalConnection object.
The Recital Universal JDBC Driver provides the same functionality for java applications.
The Recital Universal ODBC Driver provides the same functionality for applications that use ODBC.
Each of the above Client Drivers use a connection string to describe connections parameters.
The basic format of a connection string consists of a series of keyword/value pairs separated by semicolons. The equals sign (=) connects each keyword and its value.
The following table lists the valid names for keyword/values.
| Name | Default | Description |
|---|---|---|
|
Data Source |
The name or network address of the instance of the Recital Database Server which to connect to. | |
| Directory | The target directory on the remote server where data to be accessed resides. This is ignored when a Database is specified. | |
|
Encrypt |
false | When true, DES3 encryption is used for all data sent between the client and server. |
| Initial Catalog -or- Database |
The name of the database on the remote server. | |
| Password -or- Pwd |
The password used to authenticate access to the remote server. | |
| User ID | The user name used to authenticate access to the remote server. | |
|
Connection Pooling |
false | Enable connection pooling to the server. This provides for one connection to be shared. |
| Logging | false | Provides for the ability to log all server requests for debugging purposes |
| Rowid | true | When Rowid is true (the default) a column will be post-fixed to each SELECT query that is a unique row identifier. This is used to provide optimised UPDATE and DELETE operations. If you use the RecitalSqlGrid, RecitalSqlForm, or RecitalSqlGridForm components then this column is not visible but is used to handle updates to the underlying data source. |
| Logfile | The name of the logfile for logging | |
| Gateway |
Opens an SQL gateway(Connection) to a foreign SQL data source on
the remote server.
servertype@nodename:username/password-database e.g. oracle@nodename:username/password-database mysql@nodename:username/password-database postgresql@nodename:username/password-database -or- odbc:odbc_data_source_name_on_server oledb:oledb_connection_string_on_server jdbc:jdbc_driver_path_on_server;jdbc:Recital:args |
To connect to a server-side JDBC data source, you ue the gateway=value key/value pair in the following way.
gateway=jdbc:jdbc_driver_path_on_server;jdbc:Recital:args
You can find examples of connection strings for most ODBC and OLE DB data sources by clicking here.
Example in C# using the Recital Universal .NET Data Provider:
////////////////////////////////////////////////////////////////////////
// include the references below
using System.Data;
using Recital.Data;
////////////////////////////////////////////////////////////////////////
// The following code example creates an instance of a DataAdapter that
// uses a Connection to the Recital Database Server, and a gateway to
// Recital Southwind database. It then populates a DataTable
// in a DataSet with the list of customers via the JDBC driver.
// The SQL statement and Connection arguments passed to the DataAdapter
// constructor are used to create the SelectCommand property of the
// DataAdapter.
public DataSet SelectCustomers()
{
string gateway = "jdbc:/usr/java/lib/RecitalJDBC/Recital/sql/RecitalDriver;"+
"jdbc:Recital:Data Source=localhost;database=southwind";
RecitalConnection swindConn = new
RecitalConnection("Data Source=localhost;gateway=\""+gateway+"\");
RecitalCommand selectCMD = new
RecitalCommand("SELECT CustomerID, CompanyName FROM Customers", swindConn);
selectCMD.CommandTimeout = 30;
RecitalDataAdapter custDA = new RecitalDataAdapter();
custDA.SelectCommand = selectCMD;
swindConn.Open();
DataSet custDS = new DataSet();
custDA.Fill(custDS, "Customers");
swindConn.Close();
return custDS;
}
Example in Java using the Recital Universal JDBC Driver:
//////////////////////////////////////////////////////////////////////// // standard imports required by the JDBC driver import java.sql.*; import java.io.*; import java.net.URL; import java.math.BigDecimal; import Recital.sql.*; ////////////////////////////////////////////////////////////////////////
// The following code example creates a Connection to the Recital // Database Server, and a gateway to the Recital Southwind database. // It then retrieves all the customers via the JDBC driver. public void SelectCustomers() { // setup the Connection URL for JDBC String gateway = "jdbc:/usr/java/lib/RecitalJDBC/Recital/sql/RecitalDriver;"+ "jdbc:Recital:Data Source=localhost;database=southwind"; String url = "jdbc:Recital:Data Source=localhost;gateway=\""+gateway+"\";
// load the Recital Universal JDBC Driver new RecitalDriver(); // create the connection Connection con = DriverManager.getConnection(url); // create the statement Statement stmt = con.createStatement(); // perform the SQL query ResultSet rs = stmt.executeQuery("SELECT CustomerID, CompanyName FROM Customers"); // fetch the data while (rs.next()) { String CompanyID = rs.getString("CustomerID"); String CompanyName = rs.getString("CompanyName"); // do something with the data... } // Release the statement stmt.close(); // Disconnect from the server con.close(); }
There is a good article on the gluster website here which gives some good information regarding file system optimization suitable for a HA Recital cluster solution.
auth sufficient pam_krb5.so try_first_pass
auth sufficient pam_unix.so shadow nullok try_first_pass
account required pam_unix.so broken_shadow
account [default=bad success=ok user_unknown=ignore] pam_krb5.so
DirectoryIndex default.rsp index.html
The Compatibility Dialog settings are written to the compat.db file in <path>/conf - please ensure that the user setting the compatibility settings has write access to this file and directory. Once these settings are written, the dialog will not be displayed unless SET COMPATIBLE is issued.
After split brain has been detected, one node will always have the resource in a StandAlone connection state. The other might either also be in the StandAlone state (if both nodes detected the split brain simultaneously), or in WFConnection (if the peer tore down the connection before the other node had a chance to detect split brain).
At this point, unless you configured DRBD to automatically recover from split brain, you must manually intervene by selecting one node whose modifications will be discarded (this node is referred to as the split brain victim). This intervention is made with the following commands:
# drbdadm secondary resource
# drbdadm disconnect resource
# drbdadm -- --discard-my-data connect resource
On the other node (the split brain survivor), if its connection state is also StandAlone, you would enter:
# drbdadm connect resource
You may omit this step if the node is already in the WFConnection state; it will then reconnect automatically.
If all else fails and the machines are still in a split-brain condition then on the secondary (backup) machine issue:
drbdadm invalidate resource
The following example connects to a Recital ODBC datasource, executes a query then outputs all the results from the resultset.
<?php
$sql = "select country from customers limit 10";
$conn = odbc_connect('Recital ODBC test', '?', '?');
$rs = odbc_exec($conn, $sql);
odbc_result_all($rs);
odbc_close($conn);
?>
Output:
<table><tr><th>Country</th></tr>
<tr><td>Germany </td></tr>
<tr><td>Mexico </td></tr>
<tr><td>Mexico </td></tr>
<tr><td>UK </td></tr>
<tr><td>Sweden </td></tr>
<tr><td>Germany </td></tr>
<tr><td>France </td></tr>
<tr><td>Spain </td></tr>
<tr><td>France </td></tr>
<tr><td>Canada </td></tr>
</table>
For information on installing and configuring the Recital Universal ODBC Driver and creating and modifying datasources, please see the Documentation section of this web site.
Note: Use of ? for the username and password on the local server is dependent on DB_LOCAL_LOGIN being enabled.
- edit the .vmx file and add the following line
uuid.action = "keep"
- set the virtual machine to power off when vmware is stopped. Do not set this to "suspend" or it will not restart on the backup machine.
Ext3 commits writes to disk within approximately 5 seconds - Ext4 can take from 40-150 seconds. In addition, if a system is using Ext3 and crashes before the commit takes place you will still have the previous contents of a file where under Ext4 the file will be empty. Theodore Tso feels that this is a failure at the application level and that the file system is behaving as designed and as specified by the POSIX spec (which apparently does not specify what is supposed to happen when a system is not shut down cleanly). His solution to the issue is to suggest proper use of fsync() and lists various scenarios/examples in post 54 of the bug report (linked above). In addition he wrote a patch that recognize the rename() situation mentioned in his post 54 yet retains the normal Ext4 behaviors and performance in the majority of cases. Also a more "proper" solution has been provided which allows the behavior of Ext3 to be retained under Ext4 by mounting it with alloc_on_commit.
A somewhat related topic is the use of on-board caching by hard drives. This behavior can be modified on most drives by using hdparm.