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This knowledge document describes a best practice method for handling tables without primary keys or unique indexes when using Oracle GoldenGate to replicate transactional data between Oracle databases.
There is a http://blog.itpub.net/7199859/viewspace-706472/#changelog]change log at the end of this document.
In This DocumentThis document is divided into the following sections:
[list]
[*]http://blog.itpub.net/7199859/viewspace-706472/#S1]Section 1: Overview
[*]http://blog.itpub.net/7199859/viewspace-706472/#S2]Section 2: Configuring Tables without PKs or UIs
[*]http://blog.itpub.net/7199859/viewspace-706472/#S3]Section 3: References
[*]http://blog.itpub.net/7199859/viewspace-706472/#A1]Appendix A: Sample Table Configuration
Section 1: Overview1.1 Solution SummaryIn order to maintain data integrity when replicating transactional data, Oracle GoldenGate will use primary key columns or unique index columns to uniquely identify a row when issuing update or delete statements against the target database. If no primary keys or unique indexes exist on the table being replicated, Oracle GoldenGate will use all columns to uniquely identify a row.
It is perfectly acceptable to use all columns to uniquely identify a row under the following conditions:
[list]
[*]A logical key column cannot be defined for the table using the KEYCOLS parameter.
[*]No duplicate rows exist in the table
[*]Table contains a small number of rows, so full table lookups on the target database are minimal
[*]Table DML activity is very low, so "all column" table supplemental log groups do not negatively impact the source database redo logs
If the table being replicated does not meet all of the conditions listed above, it is recommended to add a column to the table with a SYS_GUID default value to uniquely identify the row. The next section describes the detailed steps on how to configure a table without a primary key or unique index in order to uniquely identify each row.
1.2 Required Software Components
[td=193]Software Component[td=149]Minimum Version
Oracle Database10.2 or greater
Oracle GoldenGate10.4 or greater

Section 2: Configuring Tables without PKs or UIs2.1 Configure Table(s) in Source DatabaseBefore instantiating the target database from a copy of source, perform. the following steps to the table(s) without primary keys or unique indexes.

Step 1 - Add Column to Table
Issue the following command to add the column to the table.
Replace with the table name being modified.
[font=NSimsun]alter table add OGG_KEY_ID raw(16);

Step 2 - Modify Column Data Default to Use SYS_GUID Values
Issue the following command to modify the OGG_KEY_ID default value to use SYS_GUID values. SYS_GUID values are unique values generated from an internal Oracle algorithm.
Immediately after modifying the OGG_KEY_ID column, newly inserted rows will automatically populate the OGG_KEY_ID column with SYS_GUID values.
Replace with the table name being modified.
[font=NSimsun]alter table with the table name being updated.
DECLARE cursor C1 is select ROWID from
where OGG_KEY_ID is null;
finished number:=0; commit_cnt number:=0; err_msg varchar2(150);
snapshot_too_old exception; pragma exception_init(snapshot_too_old, -1555);
old_size number:=0; current_size number:=0;
BEGIN
while (finished=0) loop
finished:=1;
BEGIN
for C1REC in C1 LOOP
update set GG_PK_ID = sys_guid()
where ROWID = C1REC.ROWID;
commit_cnt:= commit_cnt + 1;
IF (commit_cnt = 10000) then
commit;
commit_cnt:=0;
END IF;
END LOOP;
EXCEPTION
when snapshot_too_old then
finished:=0;
when others then
rollback;
err_msg:=substr(sqlerrm,1,150);
raise_application_error(-20555, err_msg);
END;
END LOOP;
IF(commit_cnt > 0) then
commit;
END IF;
END;
/

Note: This process could take a significant amount of time to complete based on the number of existing rows in the table. The script. will not perform. a full table lock and will only lock each row exclusively as it updates it.

Step 4 - Create Table Supplemental Log Group in Source Database
Issue the following commands in GGSCI to create the table supplemental log group using the OGG_KEY_ID column. This forces Oracle to always write the OGG_KEY_ID value to the online redo logs.
Replace with source database username.
Replace with source database user's password.
Replace with table schema owner.
Replace with the table name being modified.
[font=NSimsun]GGSCI> dblogin userid , password [font=NSimsun]GGSCI> add trandata ., COLS (OGG_KEY_ID), nokey

2.2 Configure Table in Target DatabaseStep 1 - Create Unique Index on Target Table
After instantiating the target database, issue the following command to add a unique index to the table. The unique index prevents full table scans when applying update and delete statements to the target database.
Replace with the table name the unique index is on.
Replace with tablespace name to store unique index.
[font=NSimsun]create unique index OGG__UI on (OGG_KEY_ID) logging online tablespace

Note: This process could take a significant amount of time to complete based on the number of existing rows in the table.

2.3 Oracle GoldenGate ConfigurationStep 1 - Specify OGG_KEY_ID for Table Key in Extract Parameter File
Use the KEYCOLS parameter in the Extract parameter file to define OGG_KEY_ID as the unique column for the table.
Replace with the table name the unique index is on.
[font=NSimsun]TABLE , KEYCOLS (OGG_KEY_ID);

Section 3: ReferencesFor further information about using Oracle GoldeGate, refer to the following documents available on edelivery:
[list]
[*]Oracle GoldenGate Installation and Setup Guides
Oracle GoldenGate Administration Guide [list]
[*]Introduces Oracle GoldenGate components and explains how to plan for, configure, and implement Oracle GoldenGate.
[*]Oracle GoldenGate Reference Guide [list]
[*]Provides detailed information about Oracle GoldenGate parameters, commands, and functions.
Oracle GoldenGate Troubleshooting and Performance Tuning Guide [list]
[*]Provides suggestions for improving the performance of Oracle GoldenGate in different situations, and provides solutions to common problems.
[*]

Appendix A: Sample Table ConfigurationAdd Column to TableSQL> SELECT * FROM NL_WEST;TEAM_NAME LOCATION
---------------- --------------------
PADRES SAN DIEGO
ROCKIES COLORADO
DODGERS LOS ANGELES
DIAMONDBACKS ARIZONASQL> alter table NL_WEST add OGG_KEY_ID raw(16);Table altered.SQL> select * from NL_WEST;TEAM_NAME LOCATION OGG_KEY_ID
---------------- ------------------ ----------------
PADRES SAN DIEGO
ROCKIES COLORADO
DODGERS LOS ANGELES
DIAMONDBACKS ARIZONA
Modify Column Data Default to Use SYS_GUID() ValuesSQL> alter table NL_WEST modify OGG_KEY_ID default sys_guid();Table altered.SQL> select * from NL_WEST;TEAM_NAME LOCATION OGG_KEY_ID
--------------- ------------------ ----------------
PADRES SAN DIEGO
ROCKIES COLORADO
DODGERS LOS ANGELES
DIAMONDBACKS ARIZONASQL> INSERT INTO NL_WEST (TEAM_NAME,LOCATION) VALUES ('GIANTS','SAN FRANCISCO');1 row created.SQL> COMMIT;Commit complete.SQL> select * from NL_WEST;TEAM_NAME LOCATION OGG_KEY_ID
---------------- ---------------- ----------------
PADRES SAN DIEGO
ROCKIES COLORADO
DODGERS LOS ANGELES
DIAMONDBACKS ARIZONA
GIANTS SAN FRANCISCO 95AB2831E724991FE040C8C86E0162D0
Backfill Existing Table Rows with SYS_GUID() ValuesSQL> DECLARE cursor C1 is select ROWID from
NL_WEST
where OGG_KEY_ID is null;
2 3 4 finished number:=0; commit_cnt number:=0; err_msg varchar2(150);
5 snapshot_too_old exception; pragma exception_init(snapshot_too_old, -1555);
6 old_size number:=0; current_size number:=0;
7 BEGIN
8 while (finished=0) loop
9 finished:=1;
10 BEGIN
11 for C1REC in C1 LOOP
12 update NL_WEST
13 set OGG_KEY_ID = sys_guid()
14 where ROWID = C1REC.ROWID;
15 commit_cnt:= commit_cnt + 1;
16 IF (commit_cnt = 10000) then
17 commit;
18 commit_cnt:=0;
19 END IF;
20 END LOOP;
21 EXCEPTION
22 when snapshot_too_old then
23 finished:=0;
24 when others then
25 rollback;
26 err_msg:=substr(sqlerrm,1,150);
27 raise_application_error(-20555, err_msg);
28 END;
END LOOP;
29 30 IF(commit_cnt > 0) then
31 commit;
32 END IF;
33 END;
34 /PL/SQL procedure successfully completed.SQL> select * from NL_WEST;TEAM_NAME LOCATION OGG_KEY_ID
---------------- ---------------- ----------------
PADRES SAN DIEGO 95AB2831E725991FE040C8C86E0162D0
ROCKIES COLORADO 95AB2831E726991FE040C8C86E0162D0
DODGERS LOS ANGELES 95AB2831E727991FE040C8C86E0162D0
DIAMONDBACKS ARIZONA 95AB2831E728991FE040C8C86E0162D0
GIANTS SAN FRANCISCO 95AB2831E724991FE040C8C86E0162D0
Create Table Supplemental Log Group in Source DatabaseGGSCI> dblogin userid OGG, password OGGGGSCI> add trandata MLB.NL_WEST, COLS (OGG_KEY_ID), nokey
Create Unique Index on Target TableSQL> create unique index GG_NL_WEST_UI on NL_WEST (OGG_KEY_ID) logging online;Index created.