Incorrect handling of unused columns during GoldenGate initial load using Direct Bulk Load to SQL*Loader¶
Today I faced an interesting issue performing a GoldenGate initial load with a Direct Bulk Load to SQL*Loader. The issue was related to the incorrect handling of unused columns during such loads and can cause incorrect data getting loaded into a database under certain conditions.
I tried to reproduce the issue using one database in my setup but was not able to do that, and had to use two databases instead. I used Oracle Database 12.1.0.2 with DBBP 12.1.0.2.160419 applied and GoldenGate 12.2.0.1.160419 Patch Set.
I am going to use two database in my test case - let us call them SOURCE and TARGET.
Firstly, let us create a test schema with a single table, and populate it with some data:
DBA@SOURCE> grant create session, create table, unlimited tablespace to tc identified by tc;
Grant succeeded.
DBA@SOURCE> conn tc/tc@source
Connected.
TC@SOURCE>
SQL> create table direct_load(
2 column1 int,
3 unused1 int,
4 column2 int,
5 column3 int);
Table created.
TC@SOURCE>
TC@SOURCE> insert into direct_load values (1, 0, 2, 3);
1 row created.
TC@SOURCE> commit;
Commit complete.
TC@SOURCE> select *
2 from direct_load;
COLUMN1 UNUSED1 COLUMN2 COLUMN3
---------- ---------- ---------- ----------
1 0 2 3
Secondly, set the column UNUSED1 unused:
TC@SOURCE> alter table direct_load set unused column unused1;
Table altered.
Now I will run the same DDL commands in the TARGET database, which is obviously what a GoldenGate server will do if we setup DDL replication:
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DBA@TARGET> grant create session, create table, unlimited tablespace to tc identified by tc;
Grant succeeded.
DBA@TARGET> conn tc/tc@target
Connected.
TC@TARGET> create table direct_load(
2 column1 int,
3 unused1 int,
4 column2 int,
5 column3 int);
Table created.
TC@TARGET>
TC@TARGET> insert into direct_load values (1, 0, 2, 3);
1 row created.
TC@TARGET> commit;
Commit complete.
TC@TARGET> select *
2 from direct_load;
COLUMN1 UNUSED1 COLUMN2 COLUMN3
---------- ---------- ---------- ----------
1 0 2 3
TC@TARGET>
TC@TARGET> alter table direct_load set unused column unused1;
Consider the scenario when it was decided to resynchronize data in the TARGET database from SOURCE.
I am going to remove all rows from the table in the TARGET database first:
TC@TARGET> truncate table direct_load;
Table truncated.
Proceed with GoldenGate setup.
I want to use GoldenGate Direct Bulk Load to SQL*Loader capability to move the data from the SOURCE database to TARGET.
Let us use IRTC and IETC as the names of an initial load replicat and extract correspondingly:
-- setup initial load replicat
GGSCI (ogg-test) 2> edit params irtc
-- UserIdAlias may be customized accordingly to your environment or simply use a username/password pair
Replicat irtc
AssumeTargetDefs
UserIdAlias target_ogg_replicat
DiscardFile ./dirrpt/irtc.dsc, Purge
-- I want to use Direct Bulk Load
BulkLoad
-- I used PDB "orcl" for my experiments:
Map orcl.tc.*, target orcl.tc.*;
-- setup initial load extract
GGSCI (ogg-test) 149> edit params ietc
Extract ietc
RmtHost ogg-test, MgrPort 7809
RmtTask Replicat, Group irtc
UserIdAlias source_ogg_extract
Table orcl.tc.direct_load;
-- creating GoldenGate processes
GGSCI (ogg-test) 116> add replicat irtc SpecialRun
REPLICAT added.
GGSCI (ogg-test) 117> add extract ietc SourceIsTable
EXTRACT added.
The setup is finished. Right now we can try to perform the initial load:
GGSCI (ogg-test) 15> info i*tc, tasks
EXTRACT IETC Initialized 2016-09-01 08:54 Status STOPPED
Checkpoint Lag Not Available
Log Read Checkpoint Not Available
First Record Record 0
Task SOURCEISTABLE
REPLICAT IRTC Initialized 2016-09-01 08:54 Status STOPPED
Checkpoint Lag 00:00:00 (updated 00:00:28 ago)
Log Read Checkpoint Not Available
Task SPECIALRUN
GGSCI (ogg-test) 16> start extract ietc
Sending START request to MANAGER ...
EXTRACT IETC starting
The load completed pretty soon:
GGSCI (ogg-test) 17> info i*tc, tasks
EXTRACT IETC Last Started 2016-09-01 08:55 Status STOPPED
Checkpoint Lag Not Available
Log Read Checkpoint Table ORCL.TC.DIRECT_LOAD
2016-09-01 08:55:27 Record 1
Task SOURCEISTABLE
REPLICAT IRTC Initialized 2016-09-01 08:54 Status STOPPED
Checkpoint Lag 00:00:00 (updated 00:02:09 ago)
Log Read Checkpoint Not Available
Task SPECIALRUN
The ggserr.log file does not raise any concerns:
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2016-09-01 08:55:11 INFO OGG-00987 Oracle GoldenGate Command Interpreter for Oracle: GGSCI command (velikikh): start extract ietc.
2016-09-01 08:55:11 INFO OGG-00963 Oracle GoldenGate Manager for Oracle, mgr.prm: Command received from GGSCI on host [127.0.0.1]:54562 (START EXTRACT IETC ).
2016-09-01 08:55:11 INFO OGG-00960 Oracle GoldenGate Manager for Oracle, mgr.prm: Access granted (rule #8).
2016-09-01 08:55:11 INFO OGG-01017 Oracle GoldenGate Capture for Oracle, ietc.prm: Wildcard resolution set to IMMEDIATE because SOURCEISTABLE is used.
2016-09-01 08:55:11 INFO OGG-00992 Oracle GoldenGate Capture for Oracle, ietc.prm: EXTRACT IETC starting.
2016-09-01 08:55:11 INFO OGG-03059 Oracle GoldenGate Capture for Oracle, ietc.prm: Operating system character set identified as ISO-8859-1.
2016-09-01 08:55:11 INFO OGG-02695 Oracle GoldenGate Capture for Oracle, ietc.prm: ANSI SQL parameter syntax is used for parameter parsing.
2016-09-01 08:55:12 INFO OGG-03522 Oracle GoldenGate Capture for Oracle, ietc.prm: Setting session time zone to source database time zone 'GMT'.
2016-09-01 08:55:12 WARNING OGG-00752 Oracle GoldenGate Capture for Oracle, ietc.prm: Failed to validate table ORCL.TC.DIRECT_LOAD. Likely due to existence of unused column. Please make sure you use sourcedefs in downstream Replicat, or the target table has exactly the same unused columns when using ASSUMETARGETDEFS or DDL replication.
2016-09-01 08:55:12 WARNING OGG-06439 Oracle GoldenGate Capture for Oracle, ietc.prm: No unique key is defined for table DIRECT_LOAD. All viable columns will be used to represent the key, but may not guarantee uniqueness. KEYCOLS may be used to define the key.
2016-09-01 08:55:12 INFO OGG-06509 Oracle GoldenGate Capture for Oracle, ietc.prm: Using the following key columns for source table ORCL.TC.DIRECT_LOAD: COLUMN1, COLUMN2, COLUMN3.
2016-09-01 08:55:12 INFO OGG-01851 Oracle GoldenGate Capture for Oracle, ietc.prm: filecaching started: thread ID: 7.
2016-09-01 08:55:12 INFO OGG-01815 Oracle GoldenGate Capture for Oracle, ietc.prm: Virtual Memory Facilities for: COM
anon alloc: mmap(MAP_ANON) anon free: munmap
file alloc: mmap(MAP_SHARED) file free: munmap
target directories:
/export/home/velikikh/oracle/12.2.0.1/ggs/dirtmp.
2016-09-01 08:55:16 INFO OGG-00975 Oracle GoldenGate Manager for Oracle, mgr.prm: EXTRACT IETC starting.
2016-09-01 08:55:16 INFO OGG-00993 Oracle GoldenGate Capture for Oracle, ietc.prm: EXTRACT IETC started.
2016-09-01 08:55:16 INFO OGG-00963 Oracle GoldenGate Manager for Oracle, mgr.prm: Command received from EXTRACT on host [127.0.0.1]:58728 (START REPLICAT IRTC CPU -1 PRI -1 PARAMS ).
2016-09-01 08:55:16 INFO OGG-00960 Oracle GoldenGate Manager for Oracle, mgr.prm: Access granted (rule #8).
2016-09-01 08:55:16 INFO OGG-01025 Oracle GoldenGate Delivery for Oracle: REPLICAT task started by manager (port 7810).
2016-09-01 08:55:21 INFO OGG-00963 Oracle GoldenGate Manager for Oracle, mgr.prm: Command received from RMTTASK on host [::1]:59974 (REPORT 3871 7810).
2016-09-01 08:55:21 INFO OGG-00960 Oracle GoldenGate Manager for Oracle, mgr.prm: Access granted (rule #1).
2016-09-01 08:55:21 INFO OGG-00973 Oracle GoldenGate Manager for Oracle, mgr.prm: Manager started replicat task process (Port 7810).
2016-09-01 08:55:26 INFO OGG-01229 Oracle GoldenGate Delivery for Oracle: Connected to ogg-test:50783.
2016-09-01 08:55:26 INFO OGG-00995 Oracle GoldenGate Delivery for Oracle, irtc.prm: REPLICAT IRTC starting.
2016-09-01 08:55:26 INFO OGG-03059 Oracle GoldenGate Delivery for Oracle, irtc.prm: Operating system character set identified as ISO-8859-1.
2016-09-01 08:55:26 INFO OGG-02695 Oracle GoldenGate Delivery for Oracle, irtc.prm: ANSI SQL parameter syntax is used for parameter parsing.
2016-09-01 08:55:27 INFO OGG-02679 Oracle GoldenGate Delivery for Oracle, irtc.prm: The Replicat process logged on to database ORCL and can only apply to that database.
2016-09-01 08:55:27 INFO OGG-06451 Oracle GoldenGate Delivery for Oracle, irtc.prm: Triggers will be suppressed by default.
2016-09-01 08:55:27 INFO OGG-01815 Oracle GoldenGate Delivery for Oracle, irtc.prm: Virtual Memory Facilities for: COM
anon alloc: mmap(MAP_ANON) anon free: munmap
file alloc: mmap(MAP_SHARED) file free: munmap
target directories:
/export/home/velikikh/oracle/12.2.0.1/ggs/dirtmp.
2016-09-01 08:55:27 INFO OGG-00996 Oracle GoldenGate Delivery for Oracle, irtc.prm: REPLICAT IRTC started.
2016-09-01 08:55:27 INFO OGG-03522 Oracle GoldenGate Delivery for Oracle, irtc.prm: Setting session time zone to source database time zone 'GMT'.
2016-09-01 08:55:27 INFO OGG-02911 Oracle GoldenGate Capture for Oracle, ietc.prm: Processing table ORCL.TC.DIRECT_LOAD.
2016-09-01 08:55:27 INFO OGG-06495 Oracle GoldenGate Capture for Oracle, ietc.prm: OGG created a session pool with SESSIONPOOLMAX 10, SESSIONPOOLMIN 2 and SESSIONPOOLINCR 2.
2016-09-01 08:55:27 WARNING OGG-02760 Oracle GoldenGate Delivery for Oracle, irtc.prm: ASSUMETARGETDEFS is ignored because trail file contains table definitions.
2016-09-01 08:55:27 INFO OGG-06506 Oracle GoldenGate Delivery for Oracle, irtc.prm: Wildcard MAP resolved (entry orcl.tc.*): Map "ORCL"."TC"."DIRECT_LOAD", target orcl.tc."DIRECT_LOAD".
2016-09-01 08:55:28 WARNING OGG-06439 Oracle GoldenGate Delivery for Oracle, irtc.prm: No unique key is defined for table DIRECT_LOAD. All viable columns will be used to represent the key, but may not guarantee uniqueness. KEYCOLS may be used to define the key.
2016-09-01 08:55:28 INFO OGG-02756 Oracle GoldenGate Delivery for Oracle, irtc.prm: The definition for table ORCL.TC.DIRECT_LOAD is obtained from the trail file.
2016-09-01 08:55:28 INFO OGG-06511 Oracle GoldenGate Delivery for Oracle, irtc.prm: Using following columns in default map by name: COLUMN1, COLUMN2, COLUMN3.
2016-09-01 08:55:28 INFO OGG-06510 Oracle GoldenGate Delivery for Oracle, irtc.prm: Using the following key columns for target table ORCL.TC.DIRECT_LOAD: COLUMN1, COLUMN2, COLUMN3.
2016-09-01 08:55:28 INFO OGG-00178 Oracle GoldenGate Delivery for Oracle, irtc.prm: owner = "TC", table = "DIRECT_LOAD".
2016-09-01 08:55:28 INFO OGG-00991 Oracle GoldenGate Capture for Oracle, ietc.prm: EXTRACT IETC stopped normally.
2016-09-01 08:55:33 INFO OGG-00994 Oracle GoldenGate Delivery for Oracle, irtc.prm: REPLICAT IRTC stopped normally.
Yes, there was a warning like this:
2016-09-01 08:55:12 WARNING OGG-00752 Oracle GoldenGate Capture for Oracle, ietc.prm: Failed to validate table ORCL.TC.DIRECT_LOAD. Likely due to existence of unused column. Please make sure you use sourcedefs in downstream Replicat, or the target table has exactly the same unused columns when using ASSUMETARGETDEFS or DDL replication.
But I obviously did not violate it as the source and the target table has the same unused columns.
Let us see what was actually loaded into the TARGET database:
TC@TARGET> select * from direct_load;
COLUMN1 COLUMN2 COLUMN3
---------- ---------- ----------
1 2
That is definitely not what I wanted to load and that differs from the original table in SOURCE:
TC@SOURCE> select * from direct_load;
COLUMN1 COLUMN2 COLUMN3
---------- ---------- ----------
1 2 3
Clearly the data from COLUMN2 got loaded into COLUMN3, and I did not get any errors afterwards leaving my database with "wrong" data.
That is the worst case scenario.
Originally I faced a similar issue while I was moving a bunch of data from one database to another using GoldenGate.
The load got ABENDED with ORA-01840 as in that case COLUMN3 had a DATE datatype which may be easily reproduced by the following code:
SQL> select to_date('2', 'yyyy-mm-dd hh24:mi:ss') from dual;
select to_date('2', 'yyyy-mm-dd hh24:mi:ss') from dual
*
ERROR at line 1:
ORA-01840: input value not long enough for date format
Of course, if you are lucky, you may get some other datatype conversion errors. If you are not, you may end up with wrong data in a database and it may take a while before the problem is discovered.
A few words about workarounds.
In this simple scenario, which I have written just for demonstration purposes, it was enough to drop unused columns in the TARGET database:
TC@TARGET> alter table direct_load drop unused columns;
Table altered.