Informix onlog命令详解

来源：https://www.ibm.com/docs/zh/informix-servers/12.10?topic=utilities-onlog-utility#ids_adr_0402

The onlog utility displays the contents of a logical-log
file, either on disk or on backup.

onlog: Display Logical-Log Contents

The onlog output
is useful in debugging situations when you want to track a specific
transaction or see what changes have been made to a specific tblspace.
(For information about interpreting the logical-log file contents,
see Interpreting Logical-Log Records.)

Any
user can run all of the onlog options except the -l option.
Only user informix on UNIX or
a member of the Informix-Admin group on Windows can
run the -l option.

If the database server is in offline
mode when you execute onlog, only the files on disk are read.
If the database server is in quiescent or online mode, onlog also
reads the logical-log records stored in the logical-log buffers in
shared memory (after all records on disk have been read).

When
the database server reads a logical-log file with status U from
disk while in online mode, the database server denies all access to
the logical-log files, effectively stopping database activity for
all sessions. (For more information, see onstat -l command: Print physical and logical log information.) For this reason, it
is recommended that you wait until the files have been backed up and
then read the contents of the logical-log files from backup.

The onlog utility does not have a functionally equivalent
SQL administration API command string.

当您想要跟踪特定事务或查看对特定tblspace进行了哪些更改时，联机日志输出在调试情况下很有用。（有关解释逻辑日志文件内容的信息，请参阅解释逻辑日志记录。）
任何用户都可以运行除-l选项之外的所有onlog选项。只有UNIX上的用户informix或Windows上informix Admin组的成员才能运行-l选项。
如果在执行联机时数据库服务器处于脱机模式，则只读取磁盘上的文件。如果数据库服务器处于静态或联机模式，onlog还会读取存储在共享内存中逻辑日志缓冲区中的逻辑日志记录（在读取磁盘上的所有记录之后）。
当数据库服务器在联机模式下从磁盘读取状态为U的逻辑日志文件时，数据库服务器将拒绝对逻辑日志文件的所有访问，从而有效地停止所有会话的数据库活动。（有关详细信息，请参阅onstat-l命令：打印物理和逻辑日志信息。）因此，建议您等待文件备份完成，然后从备份中读取逻辑日志文件的内容。
onlog实用程序没有功能等效的SQL管理API命令字符串。

onlog Syntax

>>-onlog--+-------------------------+--------------------------->
          |                     (1) |   
          '-|  -FILE option   |-----'   

                               (2)                                 (3)   
>--| Log-Record Read Filters |------| Log-Record Display Filters |------>

>--+-----+--+-----------+--------------------------------------><
   '- -q-'  +- -V-------+   
            '- -version-'

Notes:

1. See The -FILE option.

2. see Log-Record Read Filters

3. see Log-Record Display Filters

You direct onlog to read the following portions
of the logical log as it searches for records to display:

• Records stored on disk

• Records stored on backup media

• Records from the specified logical-log file

By default, onlog displays the logical-log record
header, which describes the transaction number and the record type.
The record type identifies the type of operation performed.

In
addition to the header, you can use the read filters to direct onlog to
display the following information:

• Logical-log record header and data (including copies of simple
  large objects stored in a dbspace or tblspace)

• Copies of blobpages from blobspaces

  They are copied from
  the logical-log backup only. They are not available from disk.

You can display every logical-log record header, or you
can specify output based on the following criteria:

• Records associated with a specific table

• Records initiated by a specific user

• Records associated with a specific transaction

If onlog detects an error in the log file, such
as an unrecognizable log type, it displays the entire log page in
hexadecimal format and terminates.

您可以指示联机日志在搜索要显示的记录时读取逻辑日志的以下部分：
存储在磁盘上的记录
存储在备份介质上的记录
指定逻辑日志文件中的记录
默认情况下，onlog显示逻辑日志记录头，其中描述了事务编号和记录类型。记录类型标识所执行操作的类型。
除了标头之外，您还可以使用读取筛选器来引导联机日志显示以下信息：
逻辑日志记录头和数据（包括存储在dbspace或tblspace中的简单大型对象的副本）
Blob空间中Blob页面的副本
它们仅从逻辑日志备份中复制。它们在磁盘上不可用。
您可以显示每个逻辑日志记录头，也可以根据以下条件指定输出：
与特定表关联的记录
由特定用户发起的记录
与特定交易相关联的记录
如果联机日志在日志文件中检测到错误，例如无法识别的日志类型，它将以十六进制格式显示整个日志页并终止。

Log-Record Read Filters

The onlog utility
uses the pathnames that are stored in the root dbspace reserved pages
to locate the logical-log files. If you use ON-Bar to
back up the logical logs, onlog asks the storage manager to
retrieve the appropriate logical-log records from the backup media.

Syntax

|--+----------------------+------------------------------------->
   '- -d--device--+-----+-'   
                  '- -b-'     

   .-------------------------------------------.   
   V                                           |   
>----+---------------------------------------+-+----------------|
     '- -n--starting_uniqid - ending_uniquid-'

Log-Record Display Filters

Syntax

   .------------------------------------------.   
   V                                          |   
|----+--------------------------------------+-+-----------------|
     |     (1)                              |     
     +- -l----------------------------------+     
     |                   (1)                |     
     +- -t--tblspace_num--------------------+     
     |               (1)                    |     
     +- -u--username------------------------+     
     |                     (1)              |     
     +- -x--transaction_id------------------+     
     |                                  (1) |     
     '- -c--compression_dictionary_file-----'

Notes:

1. Only one occurrence of this item allowed

If you do not have a compression dictionary
file, you can use an UNLOAD statement to unload the compression dictionary,
which is contained in the syscompdicts_full table in the sysmaster database,
to a compression dictionary file, as follows:

UNLOAD TO 'compression_dictionary_file'
   SELECT * FROM sysmaster:syscompdicts_full;

If you do not specify any options, onlog displays
a short listing of all the records in the log. You can combine options
with any other options to produce more selective filters. For example,
if you use both the -u and -x options, onlog displays
only the activities that the specified user initiated during the specified
transaction. If you use both the -u and -t options, onlog displays
only the activities initiated by the specified user and associated
with the specified tblspace.