What is Data instantiation
Before data replication can start, the target database must have a copy of the database objects that are going to be replicated. It is also necessary that the data for the objects to be replicated are completely in sync at the point at which the replication starts. Replication can only keep data in sync from a certain point in time, all the data before that point in time must be replicated manually as a one off task.
This is called Data Instantiation and the Oracle SCN plays a key part in this.
The Oracle SCN is captured at the point at which the replication starts to enable a snapshot of the data at a point in time. This Oracle SCN is then used in two ways:
- Everything before the SCN must be copied manually. This is the Data Instantiation and is done in this example through Oracle DataPump, but other methods are also available such as using a standby database.
- Everything after the SCN is replicated by the logical replication tool (in this case Dbvisit Replicate, but can also be Golden Gate)
Data Instantiation using DataPump over a Database Link
1. Ensure that the REPOE schema is clean. Do this by executing the record_count.bash script in the $HOME/replicate directory of the source machine. This will show you the record counts for the source and target tables but it will also show you if the target tables have not been created. (which is what you want). If there are then the DataPump script will fail.
cd $HOME/replicate ./record_count.bash TABLE_NAME TTORCL_SRC TTORCL_TRG ------------------------------ ----------- ----------- ADDRESSES 750003 *No Table* CARD_DETAILS 750003 *No Table* CUSTOMERS 500003 *No Table* INVENTORIES 900131 *No Table* LOGON 1191500 *No Table* ORDERENTRY_METADATA 4 *No Table* ORDERS 714895 *No Table* ORDER_ITEMS 2143687 *No Table* PRODUCT_DESCRIPTIONS 1000 *No Table* PRODUCT_INFORMATION 1000 *No Table* WAREHOUSES 1000 *No Table* 11 rows selected. Sum of orders TTORCL_SRC TTORCL_TRG ------------- ------------------ ------------------ ORDERS $3,572,944,731.00 $.00
The output should indicate there are no tables in the REPOE schema in the target database.
Create the Database Link
The APPLY.sh script created by the Setup Wizard for instantiating the target schema using DataPump export/import over a database link. This database link must be created for the script to work.
2. On the target server, setup the database link as the user SYSTEM pointing to the source database.
sqlplus system/manager@ttorcl_trg SQL> CREATE DATABASE LINK ttorcl_src CONNECT TO system IDENTIFIED BY manager USING 'ttorcl_src';
This database link is needed for the Datapump script that is created as APPLY.sh. The content of datapump script APPLY.sh is similar to the following. DO NOT COPY THE CONTENT. This is just an example.
impdp SYSTEM/manager@ttorcl_trg table_exists_action=TRUNCATE network_link=ttorcl_src directory=DATA_PUMP_DIR flashback_scn=564273 tables=REPOE.ADDRESSES,REPOE.CARD_DETAILS,REPOE.CUSTOMERS,REPOE.INVENTORIES,REPOE.LOGON,REPOE.ORDERENTRY_METADATA,REPOE.ORDERS,REPOE.ORDER_ITEMS,REPOE.PRODUCT_DESCRIPTIONS,REPOE.PRODUCT_INFORMATION,REPOE.WAREHOUSES logfile=REPOE_WAREHOUSES.log JOB_NAME=DP_dbvrep_XE_0001
The flashback_scn number (in this example 564273) determines the consistency point as to where the data will be loaded to. All data prior to this SCN will be loaded using the above DataPump script. All data past this SCN will be replicated using Dbvisit Replicate.
3. On the source server, as oracle, in the $HOME/dbvrep_XE directory, execute the APPLY.sh script. This script will take approximately 3 - 9 minutes to complete depending on your host machine.
cd $HOME/dbvrep_XE ./APPLY.sh
The output will be similar to:
Import: Release 11.2.0.2.0 - Production on Tue Aug 26 08:31:33 2014 Copyright (c) 1982, 2009, Oracle and/or its affiliates. All rights reserved. Connected to: Oracle Database 11g Express Edition Release 11.2.0.2.0 - 64bit Production Starting "SYSTEM"."DP_DBVREP_XE_0001": SYSTEM/********@ttorcl_trg table_exists_action=TRUNCATE network_link=ttorcl_src directory=DATA_PUMP_DIR flashback_scn=564273 tables=REPOE.ADDRESSES,REPOE.CARD_DETAILS,REPOE.CUSTOMERS,REPOE.INVENTORIES,REPOE.LOGON,REPOE.ORDERENTRY_METADATA,REPOE.ORDERS,REPOE.ORDER_ITEMS,REPOE.PRODUCT_DESCRIPTIONS,REPOE.PRODUCT_INFORMATION,REPOE.WAREHOUSES logfile=REPOE_WAREHOUSES.log JOB_NAME=DP_dbvrep_XE_0001 Estimate in progress using BLOCKS method... Processing object type TABLE_EXPORT/TABLE/TABLE_DATA Total estimation using BLOCKS method: 616.6 MB Processing object type TABLE_EXPORT/TABLE/TABLE . . imported "REPOE"."INVENTORIES" 900131 rows . . imported "REPOE"."ORDER_ITEMS" 2143687 rows . . imported "REPOE"."ORDERS" 714895 rows . . imported "REPOE"."ADDRESSES" 750003 rows . . imported "REPOE"."CUSTOMERS" 500003 rows . . imported "REPOE"."CARD_DETAILS" 750003 rows . . imported "REPOE"."LOGON" 1191500 rows . . imported "REPOE"."PRODUCT_DESCRIPTIONS" 1000 rows . . imported "REPOE"."PRODUCT_INFORMATION" 1000 rows . . imported "REPOE"."ORDERENTRY_METADATA" 4 rows . . imported "REPOE"."WAREHOUSES" 1000 rows Processing object type TABLE_EXPORT/TABLE/GRANT/OWNER_GRANT/OBJECT_GRANT Processing object type TABLE_EXPORT/TABLE/INDEX/INDEX Processing object type TABLE_EXPORT/TABLE/CONSTRAINT/CONSTRAINT Processing object type TABLE_EXPORT/TABLE/INDEX/STATISTICS/INDEX_STATISTICS Processing object type TABLE_EXPORT/TABLE/CONSTRAINT/REF_CONSTRAINT Processing object type TABLE_EXPORT/TABLE/INDEX/FUNCTIONAL_AND_BITMAP/INDEX Processing object type TABLE_EXPORT/TABLE/INDEX/STATISTICS/FUNCTIONAL_AND_BITMAP/INDEX_STATISTICS Processing object type TABLE_EXPORT/TABLE/STATISTICS/TABLE_STATISTICS Job "SYSTEM"."DP_DBVREP_XE_0001" successfully completed at 08:36:19
On the source machine, as oracle, in the $HOME/replicate directory, execute the record_count.bash script to check the record counts between the two databases.
cd $HOME/replicate ./record_count.bash TABLE_NAME TTORCL_SRC TTORCL_TRG ------------------------------ ----------- ----------- ADDRESSES 750003 750003 CARD_DETAILS 750003 750003 CUSTOMERS 500003 500003 INVENTORIES 900131 900131 LOGON 1191500 1191500 ORDERENTRY_METADATA 4 4 ORDERS 714895 714895 ORDER_ITEMS 2143687 2143687 PRODUCT_DESCRIPTIONS 1000 1000 PRODUCT_INFORMATION 1000 1000 WAREHOUSES 1000 1000 11 rows selected. Sum of orders TTORCL_SRC TTORCL_TRG ------------- ------------------ ------------------ ORDERS $3,572,944,731.00 $3,572,944,731.00
Because there was no transaction activity in the source database, the source and target database record counts should be the same.
The source and target databases are now in sync and we can start the replication processes.
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