RDBMS and listener log (xml) from SQL*Plus with V$DIAG_ALERT_EXt view
There is NO GV$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