Alert log table x$dbgalertext

Prior to 11g you had to create external table to query alert log information.

In 11g Oracle introduced X$DBGALERTEXT, which is mapped to the alert log file located at  $ORACLE_BASE/diag/rdbms/{DB_UNIQUE_NAME}/{SID}/alert/log_XX.xml.

Note that table is located in SYS schema and you need a permission to see it’s content.

So, please keep in mind this table name, it is really useful to search errors in alert log.