After logon, the main database home page comes up. The top portion of the home page enables a quick glance at important details.
Some of the most important points in the above figure have been circled and annotated with numbered references in this article. First, note the section labeled "General" (1); this section shows some most rudimentary details about the database, such as the fact that the database has been up since March 20 as well as the instance name. The Oracle Home is shown as a hyperlink, which, when clicked, shows all the products and all other Oracle databases sharing that home. The hyperlink for Listeners shows all the databases and instances registered with the listener, whose name is shown immediately below. Finally, it shows the host name (starz).
In section named "Host CPU" (2), the CPU details are shown at a glance. Section "Active Sessions" (3) shows the active sessions and what they are doing at the moment (4). We see from the above that 99% of the time spent by the sessions is in waiting. (We will find the cause of these waits later.) The section on "High Availability" (5) shows availability-related information. For example, the value of "Instance Recovery Time," which is the value of MTTR Target for the instance, determines how much time may be required for instance crash recovery.
The section on "Space Usage" (6) is interesting: it shows warnings associated with 23 segments. (Again, more on these warnings later.) The section "Diagnostic Summary" (7) provides a synopsis of database well being. The number of performance findings indicates how many issues were proactively identified by the Automatic Database Diagnostic Monitor (ADDM), the new self-diagnostic engine in 10g. EM also automatically analyzes your environment to determine if any recommended best practices are being violated; the result of this analysis is presented in the "Policy Violation" section. Finally, EM scans the alert log and shows any recent ORA errors. This information is invaluable—automatic scanning of Oracle errors in the alert log saves you the considerable trouble of manually searching for them.
The bottom part of the database home page, shown in Figure 3, we see some of these messages in more detail. The section "Alerts" (1) shows all the relevant alerts that require your attention, each of which can be easily configured. Take the first one (2), for example, which shows that the Archiver process is hanging for some reason. Of course, the next course of action is to determine why. To find out, just click on it. You will be shown more details from the alert.log file containing the error. In this case, the culprit was a filled-up flashback recovery area; we just need to clear it up so the Archiver can start working again.
