The Automatic Workload Repository (AWR) is a cornerstone of Oracle’s self-tuning capabilities, collecting and storing performance statistics for analysis. Let’s dissect each option:
A. Automatic capture of statistical information from the SGA and storing it in the AWR using Automatic Database Diagnostic.
Explanation:True. AWR automatically captures statistics (e.g., wait events, SQL stats) from the System Global Area (SGA) via the MMON (Manageability Monitor) process, storing them in the AWR repository (in SYSAUX). This is part of the Automatic Database Diagnostic Monitor (ADDM) framework, though “Automatic Database Diagnostic” likely refers to this broader mechanism.
Mechanics:Snapshots are taken hourly by default (configurable via DBMS_WORKLOAD_REPOSITORY.MODIFY_SNAPSHOT_SETTINGS), persisting data like DBA_HIST_SYSSTAT for self-tuning analysis.
Practical Use:Enables historical performance tracking, feeding tools like ADDM and SQL Tuning Advisor.
Edge Case:If STATISTICS_LEVEL=BASIC, AWR collection is disabled, haltingself-tuning.
Historical Note:Introduced in 10g, enhanced in 23ai for finer granularity.
B. ADDM, a server-based expert that reviews database performance statistics captured by Snapshots to identify potential problems before system performance degrades noticeably.
Explanation:True. The Automatic Database Diagnostic Monitor (ADDM) analyzes AWR snapshots to proactively detect issues (e.g., high CPU usage, I/O bottlenecks) and recommend fixes. It runs automatically after each snapshot in maintenance windows.
Mechanics:ADDM uses DBA_ADVISOR_FINDINGS to log issues, leveraging AWR data like DBA_HIST_SQLSTAT. Example: It might suggest adding an index for a slow query.
Practical Use:Prevents performance degradation in production systems by catching trends early.
Edge Case:Limited by snapshot frequency; real-time issues may need manual intervention.
C. Automatic Diagnostic Collector used to capture and store database errors and hung analysis.
Explanation:False. No such tool exists as an “Automatic Diagnostic Collector” in AWR context. This likely confuses the Incident Packaging Service (IPS) or ADR (Automatic Diagnostic Repository), which handles errors but isn’t AWR-based or self-tuning.
Why Incorrect:ADR collects trace files and logs, not AWR statistics, and isn’t part of self-tuning.
D. Automatic population of performance views (V$ views) from statistical data stored in AWR repository and using Automatic Database Diagnostic.
Explanation:False. V$ views (e.g., V$SESSION) are real-time memory structures in the SGA, not populated from AWR, which is historical (e.g., DBA_HIST_*). AWR doesn’t back-feed V$ views; the reverse occurs via snapshots.
Why Incorrect:Misunderstands the data flow; AWR is a sink, not a source for V$ views.
E. Automatic Application Tracing used to collect High-Load SQL statements and statistics.
Explanation:False. No “Automatic Application Tracing” exists as an AWR tool. SQL tracing (e.g., DBMS_MONITOR) is manual, and high-load SQL is captured by AWR indirectly via V$SQL snapshots, not a distinct tracing tool.
Why Incorrect:Conflates manual tracing with AWR’s passive collection.
