DMS homogeneous migrations

Question

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Hi All, I am trying out homogeneous migration MySQL on EC2 to MySQL on RDS with DMS. It is setup for Full load + CDC . Full load is fine but CDC is not working.
Source has the following setup
Values in my.cnf
[mysqld]
server-id = 1
log-bin = /var/log/mysql/mysql-bin
binlog_format = ROW
expire_logs_days = 1
binlog_row_image = FULL
log_slave_updates = TRUE
User with the following permissions.
GRANT REPLICATION SLAVE, REPLICATION CLIENT ON *.* TO ‘your_user’@‘%’;
	GRANT SELECT, RELOAD, LOCK TABLES, SHOW VIEW, EVENT, TRIGGER ON *.* TO ‘your_user’@‘%’;
GRANT BACKUP_ADMIN ON *.* TO ‘your_user’@‘%’;
Is there any config needed on RDS? I read in the documentation that target needs foreign key check disabled. Not sure this applies to homogeneous migrations.
CDC is not working and also tables migrated shows as zero but it did migrate all the tables.
Any help appreciated.

Answer

Hi Satish,
The  "load running" status means full load is still running.
Please note that DMS uses native DB engine tools for homogeneous data migrations. The migration can take hours for large databases. Wait for some more time until the full load is complete. Next the status will change to "Load complete, replication ongoing ".
Have a look at below doc for DMS Statuses of homogeneous data migrations.
https://docs.aws.amazon.com/dms/latest/userguide/dm-migrating-data-statuses.html

Answer

Hey,
DMS CDC can fail for many reasons. Please try to share more details.
Here are some general trobleshooting steps:
1. Check and understand the job status after the the Full load. 
Ref Document: https://docs.aws.amazon.com/dms/latest/userguide/CHAP_Monitoring.html#CHAP_Tasks.Status
2. Enable cloudwatch logs for the DMS task and check the log group for any errors and warning. 
Ref Document: https://repost.aws/knowledge-center/dms-task-error-status
3. If errors are on TARGET_APPLY side, check the target database error log for further information

Answer

Hi Joseph, Thanks for looking into it.

Job status is "load running". It already replicated all data from source to target. All row count in all the tables match.

![Enter image description here](/media/postImages/original/IMKDdVfUlIRkemL5XbO5G8yw)

Cloudwatch message is "Table(s) loading still in progress"
![Enter image description here](/media/postImages/original/IMaBLS-n-oToGXbVHTIDXhbA)

Answer

Joesph, It is a small database. It has migrated all the data. All row counts in all the tables match up. Its been running for a day and it has not changed status.

Answer

Ok.
In that case, thorough investigation is needed here. If you have a support plan, I suggest you to open a case AWS support.

DMS homogeneous migrations

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