Shutting down background process GTXn
In RAC Database DBA may found Auto-tuning: Shutting down background process GTXn in alert log file, which is non corruptive.
Global Transaction Process
Provides transparent support for XA global transactions in an Oracle RAC environment
These processes help maintain the global information about XA global transactions throughout the cluster. Also, the processes help perform two-phase commit for global transactions anywhere in the cluster so that an Oracle RAC database behaves as a single system to the externally coordinated distributed transactions.The GLOBAL_TXN_PROCESSES initialization parameter specifies the number of GTXn processes, where n is 0-9 or a-j. The database automatically tunes the number of these processes based on the workload of XA global transactions. You can disable these processes by setting the parameter to 0. If you try to run XA global transactions with these process disabled, an error is returned.
Its normal for the database to automatically tune the number of these processes based on the workload of XA global transactions.If any application which using XA transaction and connecting to oracle RAC database, is it required.This a normal behavior and you do not have to worry about this error messages. Ignore Them
If you are sure that you are not using XA and want to stop these messages.You can disable the GTXn background processes, then you must set GLOBAL_TXN_PROCESSES to 0 in your parameter file. Setting this parameter to 0 will disable the XA support on an Oracle RAC database.
Please refer -
Oracle® Database Reference
11g Release 2 (11.2)
Part Number E10820-02 -> GLOBAL_TXN_PROCESSES
Overview of XA Transactions and DTP Services
Oracle Database Reference 11g Release 2 (11.2)
GTXn Global Transaction Process
Oracle Real Application Clusters Administration and Deployment Guide 11g Release 2 (11.2)
Services and Distributed Transaction Processing in Oracle RAC