The ADR base is the ADR root directory. The ADR base can contain multiple ADR homes, where each ADR home is the root directory for all diagnostic data—traces, dumps, the alert log, and so on—for an instance of an Oracle product or component.
Each database has an alert log, which is an XML file containing a chronological log of database messages and errors. The alert log contents include the following:
■All internal errors (ORA-600), block corruption errors (ORA-1578), and deadlock errors (ORA-60)
■Administrative operations such as DDL statements and the SQL*Plus commands STARTUP, SHUTDOWN, ARCHIVE LOG, and RECOVER
■Several messages and errors relating to the functions of shared server and dispatcher processes
■Errors during the automatic refresh of a materialized view
A trace file is an administrative file that contains diagnostic data used to investigate problems. Also, trace files can provide guidance for tuning applications or an instance.
Each server and background process can periodically write to an associated trace file. The files information on the process environment, status, activities, and errors. The SQL trace facility also creates trace files, which provide performance information on individual SQL statements.
A dump is a special type of trace file. Whereas a trace tends to be continuous output of diagnostic data, a dump is typically a one-time output of diagnostic data in response to an event (such as an incident). When an incident occurs, the database writes one or more dumps to the incident directory created for the incident. Incident dumps also contain the incident number in the file name.
ADR stores trace files in the trace sub directory. Trace filenames are platform-dependent and use the extension .trc. Typically, database background process trace file names contain the Oracle SID, the background process name, and the operating system process number. An example of a trace file for the RECO process is my test_ reco _10355. trc.
Server process trace file names contain the Oracle SID, the string ora, and the operating system process number. An example of a server process trace filename is my test_ora_10304.trc.Sometimes trace files have corresponding trace map (.trm) files. These files contain structural information about trace files and are used for searching and navigation.