# Transfer of log files
<a name="transfer-of-log-files"></a>

DataSync is configured to periodically (every hour on the half hour mark) to move the rotated and archived metric log files from EFS to an equivalent location in S3. For details, see the [Logging](logging.md) section. This period is set through Cron schedule by `DATASYNC_METRICS_SCHEDULE = "cron(30 * * * ? *)"` and `DATASYNC_LOGS_SCHEDULE = "cron(30 * * * ? *)"`. These parameters are available through the `source/infrastructure/prebid_server/stack_constants.py` file in the solution [source code](https://github.com/aws-solutions-library-samples/prebid-server-deployment-on-aws).

After each file is copied to S3 and verified, it is removed from the EFS file system through a Lambda function. Only actively written log files are retained on the EFS.