docs/kb/gc-grace-seconds.rst
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How to change (reduce) gc_grace_seconds parameter of the table
Audience: ScyllaDB administrators
When you want to change the gc_grace_seconds parameter value for a particular table you should readjust your repairs frequency to have at
least one successful full repair for the table in question every (new) gc_grace_seconds window as discussed here <https://university.scylladb.com/courses/scylla-operations/lessons/repair-tombstones-and-scylla-manager/topic/repair-tombstones-and-scylla-manager/>_
in order to avoid data resurrection.
In addition, you should follow the procedure below in order to avoid data resurrection after the changing the gc_grace_seconds and before the next repair.
#. Run a full repair <https://manager.docs.scylladb.com/stable/repair>_ for the table in question.
#. Change the gc_grace_seconds value for the table using the :ref:ALTER table <alter-table-statement> command.
#. Verify that the schema is in sync after the change by issuing :doc:nodetool describecluster </operating-scylla/nodetool-commands/describecluster> command from all nodes.
Verify that only a single schema version is reported. Read the :doc:Schema Mismatch Troubleshooting Guide </troubleshooting/error-messages/schema-mismatch> if it's not the case.
#. Make sure that you run at least one full repair <https://manager.docs.scylladb.com/stable/repair>_ for the table in question during the gc_grace_seconds time window.
For example, if the gc_grace_seconds is set to 10 days, you should run a full repair on your tables every 8-9 days to make sure your tables are repaired before the gc_grace_seconds threshold is reached.
You can also avoid data resurrection (and hence the requirement of running the repair every gc_grace_seconds) if you make sure that tombstones are generated with operations that use Consistency Level: ALL
The operations that generate tombstones are: