在rac环境中，为了满足OGG 经典捕捉模式对分布式事务的抽取要求，

1.修改了数据库隐含参数 

  alter system set "_clusterwide_global_transactions"=false scope=spfile;

2.新加了service，并且service里边设置了DTP属性为TRUE

3.然后应用程序使用该service



参考mos文章：

GG Extract Report Shows "Purging Transaction", WARNING OGG-00723, OGG-00715, Updating I/O Checkpoint after Purging Orphaned Transactions, Has Secondary Transaction ID That Is Duplicate of Existing Open Uncommitted Transaction ( Doc ID 1458472.1 ) 



不过今天看到一篇文章：

Services and Distributed Transaction Processing in Oracle RAC(DTP) (文档 ID 1307751.1)



里边却说：

Note: 

DTP services are not needed in 11.2. 

As long as the database initialization parameter GLOBAL_TXN_PROCESSES is greater than zero,

Oracle11.2 allows different branches of the same global transaction to span multiple RAC instances.