Why is my AWS DMS replication instance in a storage-full status?

Last updated: 2019-10-03

Why is my AWS Database Migration Service (AWS DMS) replication instance in a storage-full status?

Short Description

AWS DMS replication instances have storage, and you can specify the allocated storage when you create a replication instance. By default, the dms.t2.* and dms.r4.* replication instance types have volume sizes of 50 GiB. And dms.c4.* replication instance types have volume sizes of 100 GiB. Monitor the Amazon CloudWatch metric for FreeStorageSpace to monitor the free storage space of the replication instance.

Replication instance storage is used mostly for task logs and cached changes that are collected for ongoing replication.

Migrations that have a full load only

Task logs can cause storage full issues if there are lots of task logs, for example, if you enabled detailed debug logging for a task. By default, the AWS DMS task logging level is minimal, but sometimes you need more detailed logging to determine the cause of a migration error or failure. But detailed debug logging can consume replication storage because AWS DMS writes each and every event to the log files. And too many task logs can cause your replication instance to have a storage-full status.

Migrations that have ongoing replication

Cached events can cause storage issues during a full load phase, especially if you configure your migration to use the StopTaskCachedChangesNotApplied task setting. For more information, see Creating a Replication Instance. If the storage size is too small to store the cached changes, then your replication instance has a storage-full status.

Swapped events during the change data capture (CDC) phase can cause storage issues when the changes captured from the source can't be applied to the target. AWS DMS first stores the cached events in memory, and then swaps them to storage when the values defined by the MemoryKeepTime or MemoryLimitTotal parameters are exceeded (60 seconds and 1 GiB by default, respectively). If there isn't enough storage for the swapped data, the replication instance has a storage-full status. For more information, see Change Processing Tuning Settings.

Resolution

If the replication instance is in an available status, you can delete the task logs:

  1. Open the AWS DMS console.
  2. Choose Replication instances from the navigation pane.
  3. Choose the name of the replication instance.
  4. From the Log management section, you see all the tasks and the Log size of each task.
  5. Select the tasks for which you want to delete logs, and then choose Delete.

For more information, see Managing AWS DMS Task Logs.

If the replication instance is in a storage-full status, you can't delete logs. You must increase the allocated storage size, or delete the replication task. To increase the storage size of a replication instance:

  1. Open the AWS DMS console.
  2. Choose Replication instances from the navigation pane.
  3. Choose the name of the replication instance that you want to modify the volume size for.
  4. Choose Modify.
  5. For the Allocated storage (GB) field, enter a new value.
  6. Select Apply changes immediately, and choose Modify.

Important: The allocated storage size can't be decreased after it has been increased.


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