OGG Checkpoint 详解

定位中断的位置，下次启动从中断的位置开始恢复。

1.target  端配置；

2.一条记录对应一个replicat

一. Extract Checkpoints

(1) Extract read checkpoints

(1) Startup checkpoint   --ogg启动的时候创建

当Extract 进程启动的时候，会创建startup checkpoint，用来记录此时record的相关信息。该     checkpoint    是第一个checkpoint。

startup checkpoint的统计信息包含如下内容：

(1) Thread #: 创建checkpoint 的thread编号。

(2) Sequence #:创建checkpoint 时对应的sequence 号码。  --list archive log;

(3) RBA: 创建checkpoint 时，redo log 里面record 的relative byte address。

(4)Timestamp:  创建checkpoint 时record对应的timestamp。

(5)SCN: 创建checkpoint 时 record 对应的system change number 。

(6)Redo File: 创建checkpoint 时record对应的事务日志路径。

2 ) Recovery checkpoint

recover checkpoint 记录的是data source(online redo log 或者归档中)中Extract 最久没处理的record的位置。 该checkpoint 的统计信息和startup checkpoint一样。

3) Current checkpoint

current checkpoint 是data source中Extract 最后一次读取的record的位置。

GGSCI (ogg02) 4>  info ext1

EXTRACT    EXT1      Last Started 2014-12-27 17:42   Status RUNNING

Checkpoint Lag          00:00:00 (updated 00:00:04 ago)

Process ID                31621

Log Read Checkpoint  Oracle Redo Logs

2014-12-27 18:06:05  Seqno 15, RBA 18128896

SCN 0.1142344 (1142344)

Seqno  和 RBA  会变，说明ogg是在工作的。

GGSCI (ogg02) 5>  info ext1,showch

EXTRACT    EXT1      Last Started 2014-12-27 17:42   Status RUNNING

Checkpoint Lag       00:00:00 (updated 00:00:00 ago)

Process ID           31621

Log Read Checkpoint  Oracle Redo Logs

2014-12-27 18:11:06  Seqno 15, RBA 18188800

SCN 0.1142472 (1142472)

Current Checkpoint Detail:

Read Checkpoint #1

Oracle Redo Log

Startup Checkpoint (starting position in the data source):

Thread #: 1

Sequence #: 11

RBA: 7646224

Timestamp: 2014-12-27 16:20:48.000000

SCN: 0.1136079 (1136079)

Redo File: /oradata/ogg02/redo02.log

Recovery Checkpoint (position of oldest unprocessed transaction in the data source):

Thread #: 1

Sequence #: 15

RBA: 18187792

Timestamp: 2014-12-27 18:09:41.000000

SCN: 0.1142443 (1142443)

Redo File: /oradata/ogg02/redo03.log

Current Checkpoint (position of last record read in the data source):

Thread #: 1

Sequence #: 15

RBA: 18188800

Timestamp: 2014-12-27 18:11:06.000000

SCN: 0.1142472 (1142472)

Redo File: /oradata/ogg02/redo03.log

Write Checkpoint #1

GGS Log Trail

Current Checkpoint (current write position):

Sequence #: 4

RBA: 1755

Timestamp: 2014-12-27 18:11:43.251745

Extract Trail: /u01/zt/dirdat/lt

Trail Type: RMTTRAIL

Header:

Version = 2

Record Source = A

Type = 10

# Input Checkpoints = 1

# Output Checkpoints = 1

File Information:

Block Size = 2048

Max Blocks = 100

Record Length = 2048

Current Offset = 0

Configuration:

Data Source = 3

Transaction Integrity = 1

Task Type = 0

Status:

Start Time = 2014-12-27 17:42:32

Last Update Time = 2014-12-27 18:11:43

Stop Status = A

Last Result = 400

二.Extract write checkpoints

该checkpoint包含如下信息：

(1)Sequence #: checkpoint 正在写的trail 文件的序列号。

(2)RBA: 创建checkpoint 时trail文件里record 的relative byte address。

(3)Timestamp: 创建checkpoint 时record对应的timestamp。

(4)Extract trail: trail 文件的路径。

(5)Trail Type: 标识trail 文件类型。有2个值：

EXTTRAIL：表示该trail 是本地的trail，文件由OGG进程直接写如本地disk。

RMTTRAIL：表示是远程的trail，该文件不会写入本地的磁盘，而是传到远端的的OGG上，在有远端OGG的collector 进程写disk。

比如pump 进程，里面就会写RMTTRAIL。

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target 端

GGSCI (ogg04) 1>  info rep1

REPLICAT   REP1      Last Started 2014-12-27 14:07   Status RUNNING

Checkpoint Lag         00:00:00 (updated 00:00:01 ago)

Process ID               26088

Log Read Checkpoint  File /u01/zt/dirdat/lt000004

2014-12-27 16:49:03.408880  RBA 1755

GGSCI (ogg04) 2>  info rep1,showch

REPLICAT   REP1      Last Started 2014-12-27 14:07   Status RUNNING

Checkpoint Lag         00:00:00 (updated 00:00:07 ago)

Process ID               26088

Log Read Checkpoint  File /u01/zt/dirdat/lt000004

2014-12-27 16:49:03.408880  RBA 1755

Current Checkpoint Detail:

Read Checkpoint #1

GGS Log Trail

Startup Checkpoint (starting position in the data source):

Sequence #: 3

RBA: 20259

Timestamp: 2014-12-27 14:06:57.000000

Extract Trail: /u01/zt/dirdat/lt

Current Checkpoint (position of last record read in the data source):  --最后一次读取文件的位置

Sequence #: 4

RBA: 1755

Timestamp: 2014-12-27 16:49:03.408880

Extract Trail: /u01/zt/dirdat/lt

Header:

Version = 2

Record Source = A

Type = 1

# Input Checkpoints = 1

# Output Checkpoints = 0

File Information:

Block Size = 2048

Max Blocks = 100

Record Length = 2048

Current Offset = 0

Configuration:

Data Source = 0

Transaction Integrity = -1

Task Type = 0

Database Checkpoint:

Checkpoint table = ggs.checkpoint

Key = 982417365 (0x3a8e7fd5)

Create Time = 2014-12-27 10:46:19

Status:

Start Time = 2014-12-27 14:07:31

Last Update Time = 2014-12-27 17:03:30

Stop Status = A

Last Result = 400

GGSCI (ogg04) 3> info rep1    --看rba是否有变化

REPLICAT   REP1      Last Started 2014-12-27 14:07   Status RUNNING

Checkpoint Lag       00:00:00 (updated 00:00:08 ago)

Process ID             26088

Log Read Checkpoint  File /us01/zt/dirdat/lt000004

2014-12-27 16:49:03.408880   RBA 1755

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停的时候确保两边都事物都提交了。 info 一下看看

②. data dump进程：将队列数据发送到目标

好处：① .预防网络和源库的故障；

②. 可以对数据进行过来和转换；

③.synchronize方式从多个源库上合并数据到一个中心库；

④. synchronize方式将一个源库数据传到多个目标库;

转：http://blog.csdn.net/zhengwei125/article/details/46503403