DG學習筆記(6)_LOG_ARCHIVE_DEST_N引數的各個屬性

DG學習筆記(6)_LOG_ARCHIVE_DEST_N引數的各個屬性

 

目錄

1 ARCH or LGWR

2 SYNC OR ASYNC

3 AFFIRM OR NOAFFIRM

4 DELAY,NODELAY

5 ALTERNATE, NOALTERNATE

6 DEPENDENCY, NODEPENDENCY

7 MAX_FAILURE, NOMAX_FAILURE

8 NET_TIMEOUT, NOTNET_TIMEOUT

9 REOPEN, NOREOPEN

10 TEMPLATE, NOTEMPLATE

 

1 ARCH or LGWR

 

specify that either the archiver or log writer process is responsible for transmitting redo to the standby destination. ARCH is the default. The LGWR attribute indicates that redo is transmitted to the destination oncurrently as the online redo log is written.

 

Choosing the ARCH attribute indicates that one of the archiver processes (ARCn) will create archived redo logs on the primary database and also transmit redo logs for archiving at specified destinations. This is the default setting.

 

Choosing the LGWR attribute indicates that the log writer process (LGWR) will concurrently create the archived redo logs as the online redo log is populated. Depending on the configuration, this may require the log writer process to also transmit redo logs to remote archival destinations.

(填充線上日誌的同時就生成歸檔,並傳到遠端)

 

When you set the LOG_ARCHIVE_DEST_n parameter to specify LGWR instead of ARCH, the behavior. is as follows. Instead of waiting for the online redo log to switch at the primary database and then let the archiver process write the entire archived redo log at the standby destination all at once, the log writer process creates a new redo log at the standby site that reflects the log sequence number (and size) of the current online redo log of the primary database. Then, as redo is generated at the primary database, it is also propagated to the standby database redo log file. Based on whether you specify the SYNC or ASYNC network transmission mode, the propagation will either be immediate or asynchronous.(指定LGWR時的工作原理)

 

 

2 SYNC OR ASYNC

 

Specify that network I/O operations are to be performed synchronously or asynchronously when using the LGWR. SYNC is the default.

 

SYNC:

When you specify the LGWR and SYNC attributes to transmit redo logs to multiple standby destinations, you can specify either the SYNC=PARALLEL or SYNC=NOPARALLEL option for each destination:

SYNC=PARALLEL 並行寫多個STANDBY SITE.同時寫

SYNC=NOPARALLEL 序列寫多個STANDBY SITE.一個一個寫

 

ASYNC:

ASYNC=blocks: You can specify a block count to determine the size of the SGA network buffer to be used. Block counts from 0 to 20,480 are allowed.(指定區域來臨時快取資料)

 

3 AFFIRM OR NOAFFIRM

 

specify whether log archiving disk write I/O operations on the standby database are to be performed synchronously or asynchronously. By default, disk write operations are performed asynchronously.(指定遠端的I/O寫操作是否是同步)

 

The SYNC attribute indicates that synchronous network transmission is necessary, and the AFFIRM attribute indicates that synchronous archived redo log disk write I/O

operations are necessary. Together, these attributes ensure that primary database modifications are available on the standby database.(日誌傳輸與IO操作是分離的，都必須考慮同步還是非同步的問題)

 

4 DELAY,NODELAY 延遲應用日誌 Set on Standby database

 

DELAY – number of minutes to delay application or redo, default is 30 Minutes;

NODELAY – redo applied as received, this is the default behavior.

 

 

5 ALTERNATE, NOALTERNATE

 

A destination can have a maximum of one alternate destination specified.(指定替代的路徑)

If destination fails and the REOPEN attribute is specified with a value of zero, or NOREOPEN is specified, the Oracle database server attempts to transmit the redo to the alternate destination on the next log switch. (下一次日誌切換時才嘗試傳輸到備用的路徑.)

Requires NOREOPEN or MAX_FAILURE (同時要求指定這兩個屬性)

Enabled with LOG_ARCHIVE_DEST_STATE_N=ALTERNATE

Default is NOALTERNATE

 

Example:

log_archive_dest_3=’SERVICE=stby1_path1 NOREOPEN

ALTERNATE=LOG_ARCHIVE_DEST_4’

log_archive_dest_4=’SERVICE=stby1_path2 NOREOPEN OPTIONAL’

log_archive_dest_state_3=ENABLE

log_archive_dest_state_4=ALTERNATE

 

6 DEPENDENCY, NODEPENDENCY 指定依賴性

 

Defines the destination as being dependent on the success of the other specified destination. Default is NODEPENDENCY

 

Example:

 

log_archive_dest_2='SERVICE=o9i2 LGWR SYNC AFFIRM‘

log_archive_dest_3='SERVICE=o9i1 ARCH DEPENDENCY=LOG_ARCHIVE_DEST_2’

 

7 MAX_FAILURE, NOMAX_FAILURE: 指定最大的失敗嘗試次數

 

Number of times log transport services attempts to reestablish communication.

Requires REOPEN

No Default count

NOMAX_FAILURE is default. Same as MAX_FAILURE=0

 

You can view the failure count in the FAILURE_COUNT column of the V$ARCHIVE_DEST fixed view. The related column REOPEN_SECS identifies the REOPEN attribute value

Example:

log_archive_dest_3='SERVICE=o9i1 LGWR MAX_FAILURE=30 REOPEN’

 

 

8 NET_TIMEOUT, NOTNET_TIMEOUT

 

指定網路超時的時間間隔.一旦出現超時,則FAILURE COUNT + +

 

9 REOPEN, NOREOPEN

 

指定重試間隔: Minimum number of seconds to wait before retrying a failed destination at log switch

Default is REOPEN with 300 seconds

REOPEN applies to all errors, not just connection failures. These errors include, but are not limited to, network failures, disk errors, and quota exceptions. (FAILURE的定義)

 

10 TEMPLATE, NOTEMPLATE

 

指定每個路徑儲存日誌的格式, 類似LOG_ARCHIVE_FORMAT.

Overrides standby side parameters. Therefore this cannot be used in maximum protection. The template attribute should only be used for dependent destination.

 

Example:

log_archive_dest_3='SERVICE=o9i1 . . . TEMPLATE=/fs2/arc/o9i60_%t_%s.dbf’

log_archive_dest_4='SERVICE=o9iLog . . . DEPENDENCY=LOG_ARCHIVE_DEST_3 NOREGISTER TEMPLATE=/fs2/arc/o9i60_%t_%s.dbf’