There is NO GV$DIAG_ALERT_EXT.
ADR is node,database depended and not global. Still we can use a shared ADR on a shared file system on Oracle CLusterware RAC and then is everthing from one place.
The parameter DIAGNOSTIC_DEST represents the root for the Automatic Diagnostic Repository (ADR),which includes the alertfile states. If this parameter is not set and the ORACLE_BASE is than it will use this information for the DIAGNOSTIC_DEST. If ORACLE_BASE is not set then the ADR root is in log Oracle release 11.2 has introduced new v$ diagnostic (diag) views.
select object_name from dba_objects where object_name like 'V$DIAG%' order by 1;
OBJECT_NAME
--------------------------------------------------------------------------------
V$DIAG_ADR_CONTROL
V$DIAG_ADR_INVALIDATION
V$DIAG_ALERT_EXT
V$DIAG_AMS_XACTION
V$DIAG_CRITICAL_ERROR
V$DIAG_DDE_USER_ACTION
V$DIAG_DDE_USER_ACTION_DEF
V$DIAG_DDE_USR_ACT_PARAM
V$DIAG_DDE_USR_ACT_PARAM_DEF
V$DIAG_DDE_USR_INC_ACT_MAP
V$DIAG_DDE_USR_INC_TYPE
V$DIAG_DFW_CONFIG_CAPTURE
V$DIAG_DFW_CONFIG_ITEM
V$DIAG_DIAGV_INCIDENT
V$DIAG_DIR_EXT
V$DIAG_EM_DIAG_JOB
V$DIAG_EM_TARGET_INFO
V$DIAG_EM_USER_ACTIVITY
V$DIAG_HM_FDG_SET
V$DIAG_HM_FINDING
V$DIAG_HM_INFO
V$DIAG_HM_MESSAGE
V$DIAG_HM_RECOMMENDATION
V$DIAG_HM_RUN
V$DIAG_INCCKEY
V$DIAG_INCIDENT
V$DIAG_INCIDENT_FILE
V$DIAG_INC_METER_CONFIG
V$DIAG_INC_METER_IMPT_DEF
V$DIAG_INC_METER_INFO
V$DIAG_INC_METER_PK_IMPTS
V$DIAG_INC_METER_SUMMARY
V$DIAG_INFO
V$DIAG_IPS_CONFIGURATION
V$DIAG_IPS_FILE_COPY_LOG
V$DIAG_IPS_FILE_MetaDATA
V$DIAG_IPS_PACKAGE
V$DIAG_IPS_PACKAGE_FILE
V$DIAG_IPS_PACKAGE_HISTORY
V$DIAG_IPS_PACKAGE_INCIDENT
V$DIAG_IPS_PKG_UNPACK_HIST
V$DIAG_IPS_PROGRESS_LOG
V$DIAG_IPS_REMOTE_PACKAGE
V$DIAG_PICKLEERR
V$DIAG_PROBLEM
V$DIAG_RELMD_EXT
V$DIAG_SWEEPERR
V$DIAG_VEM_USER_ACTLOG
V$DIAG_VEM_USER_ACTLOG1
V$DIAG_VHM_RUN
V$DIAG_VIEW
V$DIAG_VIEWCOL
V$DIAG_VINCIDENT
V$DIAG_VINCIDENT_FILE
V$DIAG_VINC_METER_INFO
V$DIAG_VIPS_FILE_COPY_LOG
V$DIAG_VIPS_FILE_MetaDATA
V$DIAG_VIPS_PACKAGE_FILE
V$DIAG_VIPS_PACKAGE_HISTORY
V$DIAG_VIPS_PACKAGE_MAIN_INT
V$DIAG_VIPS_PACKAGE_SIZE
V$DIAG_VIPS_PKG_FILE
V$DIAG_VIPS_PKG_INC_CAND
V$DIAG_VIPS_PKG_INC_DTL
V$DIAG_VIPS_PKG_INC_DTL1
V$DIAG_VIPS_PKG_MAIN_PROBLEM
V$DIAG_VNOT_EXIST_INCIDENT
V$DIAG_VPROBLEM
V$DIAG_VPROBLEM1
V$DIAG_VPROBLEM2
V$DIAG_VPROBLEM_BUCKET
V$DIAG_VPROBLEM_BUCKET1
V$DIAG_VPROBLEM_BUCKET_COUNT
V$DIAG_VPROBLEM_INT
V$DIAG_VPROBLEM_LASTINC
V$DIAG_VSHOWCATVIEW
V$DIAG_VSHOWINCB
V$DIAG_VSHOWINCB_I
V$DIAG_VTEST_EXISTS
V$DIAG_V_ACTINC
V$DIAG_V_ACTPROB
V$DIAG_V_INCCOUNT
V$DIAG_V_INCFCOUNT
V$DIAG_V_INC_METER_INFO_PROB
V$DIAG_V_IPSPRBCNT
V$DIAG_V_IPSPRBCNT1
V$DIAG_V_NFCINC
V$DIAG_V_SWPERRCOUNT
88 rows selected.
Describe V$DIAG_ALERT_EXT
sql> desc V$DIAG_ALERT_EXT
Name Null? Type
----------------------------------------- -------- ----------------------------
ADDR RAW(4)
INDX NUMBER
INST_ID NUMBER
ADR_PATH_IDX VARCHAR2(445)
ADR_HOME VARCHAR2(445)
ORIGINATING_TIMESTAMP TIMESTAMP(9) WITH TIME ZONE
NORMALIZED_TIMESTAMP TIMESTAMP(9) WITH TIME ZONE
ORGANIZATION_ID VARCHAR2(67)
COMPONENT_ID VARCHAR2(67)
HOST_ID VARCHAR2(67)
HOST_ADDRESS VARCHAR2(49)
MESSAGE_TYPE NUMBER
MESSAGE_LEVEL NUMBER
MESSAGE_ID VARCHAR2(67)
MESSAGE_GROUP VARCHAR2(67)
CLIENT_ID VARCHAR2(67)
MODULE_ID VARCHAR2(67)
PROCESS_ID VARCHAR2(35)
THREAD_ID VARCHAR2(67)
USER_ID VARCHAR2(67)
INSTANCE_ID VARCHAR2(67)
DETAILED_LOCATION VARCHAR2(163)
UPSTREAM_COMP_ID VARCHAR2(103)
DOWNSTREAM_COMP_ID VARCHAR2(103)
EXECUTION_CONTEXT_ID VARCHAR2(103)
EXECUTION_CONTEXT_SEQUENCE NUMBER
ERROR_INSTANCE_ID NUMBER
ERROR_INSTANCE_SEQUENCE NUMBER
MESSAGE_TEXT VARCHAR2(2051)
MESSAGE_ARGUMENTS VARCHAR2(131)
SUPPLEMENTAL_ATTRIBUTES VARCHAR2(131)
SUPPLEMENTAL_DETAILS VARCHAR2(131)
PARTITION NUMBER
RECORD_ID NUMBER
FILENAME VARCHAR2(515)
PROBLEM_KEY VARCHAR2(67)
VERSION NUMBER
Demo Output of a RAC instance
select distinct adr_home from v$diag_alert_ext;
ADR_HOME COMPONENT_ID
------------------------------------------------------- -------------------------
diag/rdbms/joord/JOORD1 rdbms
diag/rdbms/TEST/TEST1 rdbms
diag/tnslsnr/rdbms11gr2/listener_scan2 tnslsnr
diag/tnslsnr/rdbms11gr2/listener tnslsnr
diag/asm/+asm/+ASM1 rdbms
