Where operating system group OSDBA and OSOPER configured?

[oracle@rh4 ~]$ cat /u01/app/oracle/product/11.2.0/db_1/rdbms/lib/config.c

/*  SS_DBA_GRP defines the UNIX group ID for sqldba adminstrative access.  */
/*  Refer to the Installation and User's Guide for further information.  */

/* IMPORTANT: this file needs to be in sync with
              rdbms/src/server/osds/config.c, specifically regarding the
              number of elements in the ss_dba_grp array.
 */

#define SS_DBA_GRP "dba"
#define SS_OPER_GRP "oinstall"
#define SS_ASM_GRP ""

char *ss_dba_grp[] = {SS_DBA_GRP, SS_OPER_GRP, SS_ASM_GRP};