Each server and background process writes to a trace file. When a process detects an internal error, it writes information about the error to its trace file. The file name format of a trace file is sid_processname_unixpid.trc, where:

■sid is the instance system identifier

■processname is a three or four-character abbreviated process name identifying the Oracle Database process that generated the file (for example, pmon, dbwr, ora, or reco)

■unixpid is the operating system process ID number

The following is a sample trace file name:

$ORACLE_BASE/diag/rdbms/mydb/mydb/trace/test_lgwr_1237.trc

Set the MAX_DUMP_FILE initialization parameter to at least 5000 to ensure that the trace file is large enough to store error information.

Alert Files

The alert_sid.log file stores information about significant database events and messages. Events that affect the database instance or database are recorded in this file.

MAX_DUMP_FILE_SIZE参数默认为unlimited，如果生成了很大的文件，就会充满文件系统。应该设置一个比较合理的数值，以避免此类事情发生。

MAX_DUMP_FILE_SIZE参数 限定了trace files 以及alert file大小，其值1、当给具体数字时，是操作系统的数据块数。

2、当以m或k作为后缀时，表示以m或k为单位。

3、unlimited表示没有限制，只要os允许。(默认)

SQL> col name format a50;

SQL> col type format a10;

SQL> col value format a30;

SQL> show parameter max_dump_file_size;

NAME     TYPEVALUE

------------------------------------ ---------- ------------------------------

max_dump_file_size     stringUNLIMITED

修改max_dump_file_size参数：

SQL> alter system set max_dump_file_size='1024m';

System altered.

SQL> show parameter max_dump_file_size;

NAME     TYPEVALUE

------------------------------------ ---------- ------------------------------

max_dump_file_size     string1024M

SQL>

修改完成！