How is the AWR report generated in Oracle?

In Oracle databases, AWR (Automatic Workload Repository) reports are generated from performance statistics data automatically collected and stored by the database. AWR reports provide detailed information on performance metrics and activities of the database instance, which can be used for analyzing and tuning database performance.

To generate an AWR report, follow these steps:

1. The server connected to the Oracle database instance can utilize SQL*Plus or other database client tools.
2. Log in to the database instance with a user who has the necessary permissions.
3. Change the system setting to set statistics level to all.
4. Wait for a period of time for the database to collect enough AWR snapshot data (typically 30 minutes to 1 hour).
5. Please run the awr report script located at @?/rdbms/admin/awrrpt.sql.
6. Input the start time and end time according to the prompts in order to specify the time range for analysis.
7. Wait for a while until the AWR report is generated.
8. The generated AWR report will be displayed on the screen, where you can use paging commands (such as “more”) to browse through it, or export it to a text file for further analysis.

Please note that generating AWR reports requires appropriate database permissions and configurations, as well as sufficient AWR snapshot data. Additionally, generating AWR reports may have some impact on database performance, so it is recommended to perform this operation during off-peak hours.