Troubleshooting Oracle GoldenGate - Amazon Relational Database Service (original) (raw)

This section explains the most common issues when using Oracle GoldenGate with Amazon RDS for Oracle.

Topics

• Error opening an online redo log
• Oracle GoldenGate appears to be properly configured but replication is not working
• Integrated REPLICAT slow due to query on SYS."_DBA_APPLY_CDR_INFO"

Error opening an online redo log

Make sure that you configure your databases to retain archived redo logs. Consider the following guidelines:

• Specify the duration for log retention in hours. The minimum value is one hour.
• Set the duration to exceed any potential downtime of the source DB instance, any potential period of communication, and any potential period of networking issues for the source DB instance. Such a duration lets Oracle GoldenGate recover logs from the source DB instance as needed.
• Ensure that you have sufficient storage on your instance for the files.

If you don't have log retention enabled, or if the retention value is too small, you receive an error message similar to the following.

2022-03-06 06:17:27  ERROR   OGG-00446  error 2 (No such file or directory) 
opening redo log /rdsdbdata/db/GGTEST3_A/onlinelog/o1_mf_2_9k4bp1n6_.log for sequence 1306 
Not able to establish initial position for begin time 2022-03-06 06:16:55. 

Oracle GoldenGate appears to be properly configured but replication is not working

For pre-existing tables, you must specify the SCN that Oracle GoldenGate works from.

To fix this issue

1. Log in to the source database and launch the Oracle GoldenGate command line interface (ggsci). The following example shows the format for logging in.

dblogin userid oggadm1@OGGSOURCE  

1. Using the ggsci command line, set up the start SCN for theEXTRACT process. The following example sets the SCN to 223274 for the EXTRACT.

ALTER EXTRACT EABC SCN 223274  
start EABC  

1. Log in to the target database. The following example shows the format for logging in.

dblogin userid oggadm1@OGGTARGET  

1. Using the ggsci command line, set up the start SCN for theREPLICAT process. The following example sets the SCN to 223274 for the REPLICAT.

start RABC atcsn 223274  

Integrated REPLICAT slow due to query on SYS."_DBA_APPLY_CDR_INFO"

Oracle GoldenGate Conflict Detection and Resolution (CDR) provides basic conflict resolution routines. For example, CDR can resolve a unique conflict for an INSERT statement.

When CDR resolves a collision, it can insert records into the exception table_DBA_APPLY_CDR_INFO temporarily. Integrated REPLICAT deletes these records later. In a rare scenario, the integrated REPLICAT can process a large number of collisions, but a new integrated REPLICAT does not replace it. Instead of being removed, the existing rows in_DBA_APPLY_CDR_INFO are orphaned. Any new integrated REPLICAT processes slow down because they are querying orphaned rows in _DBA_APPLY_CDR_INFO.

To remove all rows from _DBA_APPLY_CDR_INFO, use the Amazon RDS procedurerdsadmin.rdsadmin_util.truncate_apply$_cdr_info. This procedure is released as part of the October 2020 release and patch update. The procedure is available in the following database versions:

• Version 21.0.0.0.ru-2022-01.rur-2022-01.r1 and higher
• Version 19.0.0.0.ru-2020-10.rur-2020-10.r1 and higher

The following example truncates the table _DBA_APPLY_CDR_INFO.

SET SERVEROUTPUT ON SIZE 2000
EXEC rdsadmin.rdsadmin_util.truncate_apply$_cdr_info;