# Schedule a crawler to keep the AWS Glue Data Catalog and Amazon S3 in sync
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AWS Glue crawlers can be set up to run on a schedule or on demand. For more information, see [Time-based schedules for jobs and crawlers](https://docs.aws.amazon.com/glue/latest/dg/monitor-data-warehouse-schedule.html) in the *AWS Glue Developer Guide*.

If you have data that arrives for a partitioned table at a fixed time, you can set up an AWS Glue crawler to run on schedule to detect and update table partitions. This can eliminate the need to run a potentially long and expensive `MSCK REPAIR` command or manually run an `ALTER TABLE ADD PARTITION` command. For more information, see [Table partitions](https://docs.aws.amazon.com/glue/latest/dg/tables-described.html#tables-partition) in the *AWS Glue Developer Guide*.