Setting up a Classic Capture Extract process_Oracle Goldengate 11g Complete Cookbook-QQ阅读男生历史网

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Setting up a Classic Capture Extract process

A GoldenGate Classic Capture Extract process runs on the source system. This process can be configured for initially loading the source data and for continuous replication. This process reads the redo logs in the source database and looks for changes in the tables that are defined in its configuration file. These changes are then written into a buffer in the memory. When the extract reads a commit command in the redo logs, the changes for that transaction are then flushed to the trail files on disk. In case it encounters a rollback statement for a transaction in the redo log, it discards the changes from the memory. This type of Extract process is available on all platforms which GoldenGate supports. This process cannot read the changes for compressed objects. In this recipe you will learn how to set up a Classic Capture process in a GoldenGate instance.

Getting ready

Before adding the Classic Capture Extract process, ensure that you have completed the following steps in the source database environment:

Enabled database minimum supplemental logging.
Enabled supplemental logging for tables to be replicated.
Set up a manager instance.
Created a directory for the source trail files.
Decided a two-letter initial for naming the source trail files.

How to do it…

The following are the steps to configure a Classic Capture Extract process in the source database:

From the GoldenGate Home directory, run the GoldenGate software command line interface (GGSCI) as follows:
```
./ggsci
```
Edit the Extract process configuration as follows:
```
EDIT PARAMS EGGTEST1
```

This command will open an editor window. You need to add the extract configuration parameters in this window as follows:

EXTRACT <EXTRACT_NAME>
USERID <SOURCE_GG_USER>@SOURCEDB, PASSWORD ******
EXTTRAIL <specification>
TABLE <replicated_table_specification>;

For example:

EXTRACT EGGTEST1
USERID GGATE_ADMIN@DBORATEST, PASSWORD ******
EXTTRAIL /u01/app/ggate/dirdat/st
TABLE scott.*;

Save the file and exit the editor window.

Add the Classic Capture Extract to the GoldenGate instance as follows:

ADD EXTRACT <EXTRACT_NAME>, TRANLOG, <BEGIN_SPEC>

For example:

ADD EXTRACT EGGTEST1, TRANLOG, BEGIN NOW

Add the local trail to the Classic Capture configuration as follows:
```
ADD EXTTRAIL /u01/app/ggate/dirdat/st, EXTRACT EGGTEST1
```
Start the Classic Capture Extract process as follows:
```
GGSCI> START EXTRACT EGGTEST1
```

How it works…

In the preceding steps we have configured a Classic Capture Extract process to replicate all tables for a SCOTT user. For this we first configure an Extract process parameter file and add the configuration parameter to it. Once the parameter file is created, we then add the Extract process to the source manager instance. This is done using the ADD EXTRACT command in step 5. In step 6, we associate a local trail file with the Extract process and then we start it. When you start the Extract process you will see the following output:

GGSCI (prim1-ol6-112.localdomain) 11> start extract EGGTEST1
Sending START request to MANAGER ...
EXTRACT EGGTEST1 starting

You can check the status of the Extract process using the following command:

GGSCI (prim1-ol6-112.localdomain) 10> status extract EGGTEST1
EXTRACT EGGTEST1: STARTED

There's more…

There are a few additional parameters that can be specified in the extract configuration as follows:

EOFDELAY secs: This parameter controls how often GoldenGate should check the source database redo logs for new data
MEGABYTES <N>: This parameter controls the size of the extract trail file
DYNAMICRESOLUTION: Use this parameter to enable extract to build the metadata for each table when the extract encounters its changes for the first time.

If your source database ie this parameter to enable extract to build the metadata for each table when the exs a very busy OLTP production system and you cannot afford to add additional load of GoldenGate process on it, you can however offload GoldenGate processing to another server by adding some extra configuration. You will need to configure the source database to ship the redo logs to a standby site and set up a GoldenGate manager instance on that server. The Extract processes will be configured to read from the archived logs on the standby system. For this you specify an additional parameter as follows:

TRANLOGOPTIONS ARCHIVEDLOGONLY ALTARCHIVEDLOGDEST <path>

Tip

If you are using Classic Capture in ALO mode for the source database using ASM, you must store the archive log files on the standby server outside ASM to allow Classic Capture Extract to read them.