1Z0-031.3 - 5. 诊断文件（alert files, backgroud trace files, user trace files）

Diagnostic Files

Diagnostic files are a means to capture information about the database's activities.

Types:

-- alertSID.log file : Information for day-to-day operation of the database

-- Background trace files : Vital information when background processes, such as SMON, PMON, DBWn, and others fail.

-- User trace files : Vital information for fatal user errors or user forced traced files.

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Alert Log File

The alertSID.log file records the commands and Results of major events while the database is operational. 这主要包括Oracle的内部错误、数据块损坏错误、特权用户操作（例如启动例程、关闭例程、备份和恢复等）、数据库物理结构变化等信息。其信息由服务器进程和后台进程DBWR、LGWR写入。

-- Each entry has a time stamp associated with it.

-- The DBA manages the alertSID.log file.

-- Its location is defined by BACKGROUND_DUMP_DEST.

The alert log file keeps a record of the following information:

-- When the database was started or shut down

-- A list of all non-default initialization parameters

-- The startup of background processes

-- The thread being used by the instance

-- The log sequence number LGWR is writing to

-- Information regarding a log switch

-- Creation of tablespaces and undo segments

-- Alter statements that have been issued

-- Information regarding error messages such as ORA-600 and extent errors.

Background Trace Files

-- They are created when a background process encounters an errors

-- Their location is defined by BACKGROUND_DUMP_DEST

User Trace File

-- It can also be generated by a you or a server process.

-- Its location is defined by USER_DUMP_DEST.

-- Its size is defined by MAX_DUMP_FILE_SIZE and defaults to 10M.

Enabling or Disabling User Tracing

User tracing is enabled or disabled at the session or instance level by using the following commands and parameter:

- Session level using the ALTER SESSION command:

-- ALTER SESSION SET SQL_TRACE = TRUE;

- Session level by executing DBMS procedure:

-- dbms_system.SET_SQL_TRACE_IN_SESSION

- Instance level by setting the initialization parameter:

-- SQL_TRACE = TRUE

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