Overview of Diagnostic Files
Oracle Database includes a fault diagnosability infrastructure for preventing, detecting, diagnosing, and resolving database problems. Problems include critical errors such as code bugs, metadata corruption, and customer data corruption. The goals of the advanced fault diagnosability infrastructure are the following:
Detecting problems proactively
Limiting damage and interruptions after a problem is detected
Reducing problem diagnostic and resolution time
Simplifying customer interaction with Oracle Support
Automatic Diagnostic Repository
Automatic Diagnostic Repository (ADR) is a file-based repository that stores database diagnostic data such as trace files, the alert log, and Health Monitor reports. Key characteristics of ADR include:
Unified directory structure
Consistent diagnostic data formats
Unified tool set
ADR is located outside the database, which enables Oracle Database to access and manage ADR when the physical database is unavailable. An instance can create ADR before a database has been created.
Problems and Incidents
ADR proactively tracks problems, which are critical errors in the database. Critical errors manifest as internal errors, such as ORA-600, or other severe errors. Each problem has a problem key, which is a text string that describes the problem. When a problem occurs multiple times, ADR creates a time-stamped incident for each occurrence. An incident is uniquely identified by a numeric incident ID. When an incident occurs, ADR sends an incident alert to Enterprise Manager. Diagnosis and resolution of a critical error usually starts with an incident alert. Because a problem could generate many incidents in a short time, ADR applies flood control to incident generation after certain thresholds are reached. A flood-controlled incident generates an alert log entry, but does not generate incident dumps. In this way, ADR informs you that a critical error is ongoing without overloading the system with diagnostic data.