內容包括：系統內部錯誤(Ora-600)；數據塊損壞(Ora-1578,Ora-1498)；影響數據庫結構，初始化參數等的操作記錄；Instance啓動時記錄所有非默認值的初始化參數；
（如果初始化參數log_checkpoints_to_alert設置爲true，則還會記錄checkpoit的開始和結束時間，未完成的checkpoint，歸檔日誌需要的時間，實例恢復的開始和結束時間等）
官方說明：
The alert log is a chronological log of messages and errors, and
includes the following items:
All internal errors (ORA-00600), block corruption errors (ORA-01578), and deadlock errors (ORA-00060) that occur
Administrative operations, such as CREATE, ALTER, and DROP statements and STARTUP, SHUTDOWN, and ARCHIVELOG statements
Messages and errors relating to the functions of shared server and dispatcher processes
Errors occurring during the automatic refresh of a materialized view
The values of all initialization parameters that had nondefault values at the time the database and instance start
Oracle Database uses the alert log to record these operations as an alternative to displaying the information on an operator's console (although some systems also
display information on the console). If an operation is successful, a "completed" message is written in the alert log, along with a timestamp.