You should configure GTM proxy in you Postgres-XC cluster to reconnect to the new GTM.
GTM proxy does not maintain any persistent data other than the configuration file and you should just restart GTM proxy when crashed. Please visit [Real_Server_Configuration] page.
With default configuration, GTM proxy will stop when it detects error in the communication with GTM. To reconnect to the new GTM, GTM proxy need to be configured to wait for reconnect command. You can do this as follows:
[main]$ ssh node01 [node01]$ cat >> /home/postgresxc/pgxc/gtm_proxy/gtm_proxy.conf
Postgres-XC: High_Availability
Postgres-XC: Real_Server_Configuration