Comment 1 for bug 1280280

Confirmed with 5.5.37 and 5.6.19. Even as per doc, the scope is global.

http://www.percona.com/doc/percona-xtradb-cluster/5.6/wsrep-system-index.html#wsrep_replicate_myisam
http://www.percona.com/doc/percona-xtradb-cluster/5.5/wsrep-system-index.html#wsrep_replicate_myisam

On PXC 5.5.37,

[root@percona-pxc55-1 mysql]# mysql -uroot -p
Enter password:
Server version: 5.5.37-35.0-55-log Percona XtraDB Cluster (GPL), Release rel35.0, Revision 759, WSREP version 25.10, wsrep_25.10.r3985

mysql> show global variables like 'wsrep_replicate_myisam';
+------------------------+-------+
| Variable_name | Value |
+------------------------+-------+
| wsrep_replicate_myisam | OFF |
+------------------------+-------+
1 row in set (0.00 sec)

mysql> SET wsrep_replicate_myisam = ON;
ERROR 1229 (HY000): Variable 'wsrep_replicate_myisam' is a GLOBAL variable and should be set with SET GLOBAL
mysql>

On PXC 5.6.19,

root@deb-pxc56-1:~# mysql -uroot -p
Enter password:
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 8
Server version: 5.6.19-67.0-56-log Percona XtraDB Cluster (GPL), Release 25.6, wsrep_25.6.r4111

mysql> show global variables like 'wsrep_replicate_myisam';
+------------------------+-------+
| Variable_name | Value |
+------------------------+-------+
| wsrep_replicate_myisam | OFF |
+------------------------+-------+
1 row in set (0.01 sec)

mysql> SET wsrep_replicate_myisam = ON;
ERROR 1229 (HY000): Variable 'wsrep_replicate_myisam' is a GLOBAL variable and should be set with SET GLOBAL
mysql>