XA Datasource in Microsoft JDBC driver and jTDS JDBC Driver

Question

I'm a little new to SQL Server, and working in a java application connecting to it. I found these 2 well-known JDBC drivers, microsoft one and jTDS one. I'm trying to use XA datasource.

According to Microsoft documentation, here it says I have to configure server, before using XA datasource. According to this doc, what it asks to do is to enable XA in the server.

But I don't see any such server-side modification required for jTDS. (I couldn't find any doc saying so, here)

So, my question is how does jTDS itself manage to enable XA in server, while Microsoft one needs me to do the enabling task?

Or am I missing something here?

Answer 1

Found the answer after digging in jTDS driver distribution. It has README.XA file saying it all. Copying the content below.

XA support in jTDS
==================

This version of jTDS includes a XADataSource class which allows the driver to
be used with J2EE servers that only support XA JDBC connections. The class name
is net.sourceforge.jtds.jdbcx.JtdsDataSource.

By default the driver will emulate distributed transactions fooling the J2EE
environment into believing that two phase commit is supported. This emulation
has the serious drawback that when used in a true distributed environment, the
driver may not be able to commit or rollback when requested by the transaction
manager. In this situation data loss or corruption can occur.

In general this emulation is safe to use when jTDS is the only transactional
resource manager or where the database is read only and never updated.
Emulation is much faster than support for true distributed transactions and
this may be another reason to consider using the driver in this mode if the
risks are understood.

Many J2EE servers provide their own XA emulations that allow the normal
net.sourceforge.jtds.jdbc.Driver to be used. The recommendation is to use the
vendor's emulation, if available, rather than the XADataSource as this
configuration is likely to be more stable.

The driver will support true distributed transactions with MS SQL2000 provided
that the extended stored procedure in JtdsXA.dll is installed in the target
server. To disable the XA emulation and use the stored procedure, set the
connection property "xaemulation" to "false". This implementation is very
immature and cannot be recommended for production use at this stage. It may
however be useful for development when true two phase commit support is
required.

Another connection property, "LogFile" has been added to JtdsDataSource which
allows the jTDS logging to be enabled in a J2EE environment. The parameter
value specifies the output file path for the logging information.

Two example configurations for the popular JBoss server are included in the
conf directory. One configuration uses the Driver interface and the server's XA
emulation the other shows how to use the driver's XA support in either emulated
or real mode.


Installing JtdsXA.dll
=====================

For true distributed transaction support JtdsXA.dll has to be installed on the
server. The installation procedure consists of two simple steps:

 1. Copy JtdsXA.dll from the XA directory to the <SQL_Server_Root>/binn
    directory of the SQL Server installation.

 2. From the command prompt run the following command in the directory where
    you extracted jTDS:

    isql -Usa -P<sa_password> -S<server_name_or_ip> -iXA\instjtds.sql

    Alternatively, use any DB tool (such as Query Analyzer or any JDBC tool) to
    execute the script within the 'master' database. Don't forget to log in as
    'sa'.

This will install the xp_jtdsxa extended stored procedure, used by jTDS to
provide true distributed transacition support.

Answer 2

You would use the sqljdbc_4.0 driver ( http://www.microsoft.com/en-us/download/details.aspx?id=11774 ). Here explain XA Datasource and how enabled this in the server.. this works for me.

-- This script installs the extended stored procedures that implement
-- distributed transaction and XA support for the Microsoft JDBC Driver 4.0 for SQL Server.
-- Works only with SQL 2005 and above

-- Notes for SQL Administrators:

-- #1. Prior to running this script you must copy the extended stored procedure dll SQLJDBC_XA.dll 
--     to the target SQL Server's Binn folder.

-- #2. Permissions to the distributed transaction support procedures for the Microsoft JDBC Driver 4.0 
--     for SQL Server are granted through the SQL Server role [SqlJDBCXAUser].  To maintain a secure default 
--     configuration, no user is granted access to this role by default.

-- Drop and re-create the extended stored procedure definitions in master.

use master
go

-- Drop any existing procedure definitions.
if exists (select * from sys.objects where object_id = object_id('xp_sqljdbc_xa_init') and OBJECTPROPERTY(object_id, N'IsExtendedProc') = 1) exec sp_dropextendedproc 'xp_sqljdbc_xa_init' 
if exists (select * from sys.objects where object_id = object_id('xp_sqljdbc_xa_start') and OBJECTPROPERTY(object_id, N'IsExtendedProc') = 1) exec sp_dropextendedproc 'xp_sqljdbc_xa_start'
if exists (select * from sys.objects where object_id = object_id('xp_sqljdbc_xa_end') and OBJECTPROPERTY(object_id, N'IsExtendedProc') = 1) exec sp_dropextendedproc 'xp_sqljdbc_xa_end'
if exists (select * from sys.objects where object_id = object_id('xp_sqljdbc_xa_prepare') and OBJECTPROPERTY(object_id, N'IsExtendedProc') = 1) exec sp_dropextendedproc 'xp_sqljdbc_xa_prepare'
if exists (select * from sys.objects where object_id = object_id('xp_sqljdbc_xa_commit') and OBJECTPROPERTY(object_id, N'IsExtendedProc') = 1) exec sp_dropextendedproc 'xp_sqljdbc_xa_commit'
if exists (select * from sys.objects where object_id = object_id('xp_sqljdbc_xa_rollback') and OBJECTPROPERTY(object_id, N'IsExtendedProc') = 1) exec sp_dropextendedproc 'xp_sqljdbc_xa_rollback'
if exists (select * from sys.objects where object_id = object_id('xp_sqljdbc_xa_forget') and OBJECTPROPERTY(object_id, N'IsExtendedProc') = 1) exec sp_dropextendedproc 'xp_sqljdbc_xa_forget'
if exists (select * from sys.objects where object_id = object_id('xp_sqljdbc_xa_recover') and OBJECTPROPERTY(object_id, N'IsExtendedProc') = 1) exec sp_dropextendedproc 'xp_sqljdbc_xa_recover'
if exists (select * from sys.objects where object_id = object_id('xp_sqljdbc_xa_rollback_ex') and OBJECTPROPERTY(object_id, N'IsExtendedProc') = 1) exec sp_dropextendedproc 'xp_sqljdbc_xa_rollback_ex'
if exists (select * from sys.objects where object_id = object_id('xp_sqljdbc_xa_forget_ex') and OBJECTPROPERTY(object_id, N'IsExtendedProc') = 1) exec sp_dropextendedproc 'xp_sqljdbc_xa_forget_ex'
if exists (select * from sys.objects where object_id = object_id('xp_sqljdbc_xa_prepare_ex') and OBJECTPROPERTY(object_id, N'IsExtendedProc') = 1) exec sp_dropextendedproc 'xp_sqljdbc_xa_prepare_ex'
if exists (select * from sys.objects where object_id = object_id('xp_sqljdbc_xa_init_ex') and OBJECTPROPERTY(object_id, N'IsExtendedProc') = 1) exec sp_dropextendedproc 'xp_sqljdbc_xa_init_ex'
go

-- Install the procedures.
exec sp_addextendedproc 'xp_sqljdbc_xa_init', 'SQLJDBC_XA.dll'
exec sp_addextendedproc 'xp_sqljdbc_xa_start', 'SQLJDBC_XA.dll'
exec sp_addextendedproc 'xp_sqljdbc_xa_end', 'SQLJDBC_XA.dll'
exec sp_addextendedproc 'xp_sqljdbc_xa_prepare', 'SQLJDBC_XA.dll'
exec sp_addextendedproc 'xp_sqljdbc_xa_commit', 'SQLJDBC_XA.dll'
exec sp_addextendedproc 'xp_sqljdbc_xa_rollback', 'SQLJDBC_XA.dll'
exec sp_addextendedproc 'xp_sqljdbc_xa_forget', 'SQLJDBC_XA.dll'
exec sp_addextendedproc 'xp_sqljdbc_xa_recover', 'SQLJDBC_XA.dll'
exec sp_addextendedproc 'xp_sqljdbc_xa_rollback_ex', 'SQLJDBC_XA.dll'
exec sp_addextendedproc 'xp_sqljdbc_xa_forget_ex', 'SQLJDBC_XA.dll'
exec sp_addextendedproc 'xp_sqljdbc_xa_prepare_ex', 'SQLJDBC_XA.dll'
exec sp_addextendedproc 'xp_sqljdbc_xa_init_ex', 'SQLJDBC_XA.dll'
go

-- Create the [SqlJDBCXAUser] role in master database.
-- The SQL administrator can later add users to this role to allow users to participate 
-- in Microsoft JDBC Driver 4.0 for SQL Server distributed transactions.
if exists (select * from sys.schemas where name = 'SqlJDBCXAUser' ) 
drop schema [SqlJDBCXAUser];

if exists (select * from sys.database_principals where name = 'SqlJDBCXAUser' and type='R') 
drop role [SqlJDBCXAUser];

create role [SqlJDBCXAUser]
go


-- Grant privileges to [SqlJDBCXAUser] role to the extended stored procedures.
grant execute on xp_sqljdbc_xa_init to [SqlJDBCXAUser]
grant execute on xp_sqljdbc_xa_start to [SqlJDBCXAUser]
grant execute on xp_sqljdbc_xa_end to [SqlJDBCXAUser]
grant execute on xp_sqljdbc_xa_prepare to [SqlJDBCXAUser]
grant execute on xp_sqljdbc_xa_commit to [SqlJDBCXAUser]
grant execute on xp_sqljdbc_xa_rollback to [SqlJDBCXAUser]
grant execute on xp_sqljdbc_xa_recover to [SqlJDBCXAUser]
grant execute on xp_sqljdbc_xa_forget to [SqlJDBCXAUser]
grant execute on xp_sqljdbc_xa_rollback_ex to [SqlJDBCXAUser]
grant execute on xp_sqljdbc_xa_forget_ex to [SqlJDBCXAUser]
grant execute on xp_sqljdbc_xa_prepare_ex to [SqlJDBCXAUser]
grant execute on xp_sqljdbc_xa_init_ex to [SqlJDBCXAUser]
go

-- Add users to the [SqlJDBCXAUser] role as needed.

-- Example for adding a SQL authentication user to the SqlJDBCXAUser role.
-- exec sp_addrolemember [SqlJDBCXAUser], 'MySQLUser'

-- Example for adding a windows domain user to the SqlJDBCXAUser role.
-- exec sp_addrolemember [SqlJDBCXAUser], 'MyDomain\MyWindowsUser'

print ''
print 'SQLJDBC XA DLL installation script complete.'
print 'Check for any error messages generated above.'