GLOBAL_TXN_PROCESSES 参数与 分布式事务，DTP 属性

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.