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Questions tagged with Oracle Migrations

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DMS CDC task (Oracle->S3, binary reader) "hangs" without failing, misses changes

We're running DMS on an on-prem Oracle database, with a destination to S3 (which we then load to Snowflake outside of DMS). We're finding the replication task will, seemingly at random times after working fine for a few hours, simply stop processing Oracle log files and so will report no source CDC changes, and will report zero latency (whereas the source latency generally fluctuates between 1 and 5s). Cloudwatch logs continue to show the heartbeat message (but few other messages do): ```[SORTER ]I: Task is running (sorter.c:736)``` After turning on DEBUG logging, we're seeing the following messages that appear to be related to this problem: ``` 2021-12-27T16:39:50:430405 [TASK_MANAGER ]D: There are 284 swap files of total size 1 Mb. Left to process 5 of size 1 Mb (replicationtask_cmd.c:1639) ``` And this error, which seemingly pops up much more frequently, so including it here, but not sure if it's related: ``` 2021-12-27T16:43:01:094411 [DATA_STRUCTURE ]E: SQLite general error. Code <19>, Message <UNIQUE constraint failed: events.identifier, events.eventType, events.detailMessage>. [1000506] (at_sqlite.c:475) ``` We're running a dms.r5.large, and can't otherwise find any patterns about when/why the issue appears (again, without any warnings, other errors, etc.). Restarting the task (stopping the task takes an unusually long time) fixes the problem and causes the task to "catch up" to where the updates stalled. Our current workaround is to set an alert looking for too-long a time of zero latency, and then having a lambda function stop and restart the task.
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asked 9 months ago
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