# Does tombstone blocks shadowed data SSTables from being purged in TWCS

**URL:** <https://forum.scylladb.com/t/does-tombstone-blocks-shadowed-data-sstables-from-being-purged-in-twcs/3205>\
**Category:** ScyllaDB\
**Tags:** compaction, repair, sstable, tombstone\
**Created:** [November 18, 2024, 5:23pm UTC](https://forum.scylladb.com/t/does-tombstone-blocks-shadowed-data-sstables-from-being-purged-in-twcs/3205 "2024-11-18T17:23:58Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Artem\_Golovko](https://sea2.discourse-cdn.com/flex016/user_avatar/forum.scylladb.com/artem_golovko/32/1290_2.png) [@Artem\_Golovko](https://forum.scylladb.com/u/Artem_Golovko)\
**Post date:** [November 18, 2024, 5:23pm UTC](https://forum.scylladb.com/t/does-tombstone-blocks-shadowed-data-sstables-from-being-purged-in-twcs/3205/1 "2024-11-18T17:23:58Z")

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_Installation details_  
ScyllaDB version: 6.2.1

**From the documentation** : Avoid overwriting data and deleting data explicitly at all costs, as this can potentially block an expired SSTable from being purged, due to the checks that are performed to avoid data resurrection.

> **[Compaction | ScyllaDB Docs](https://opensource.docs.scylladb.com/stable/kb/compaction.html#time-window-compaction-strategy-twcs)**
>
> ScyllaDB is an Apache Cassandra-compatible NoSQL data store that can handle 1 million transactions per second on a single server.

**Question** :  
I have tombstone in one windowed SSTable A, but actual shadowed data in SSTable B (or others as well). Will tombstone in SSTable A block purging of SSTable B (where is shadowed data is stored) and why if it so? Or documentation means that it will block purging of SSTable A (where is tombstone is stored) because we need to wait tombstone expiration (gc\_grace\_seconds/repair/etc)?

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**Author:** ![Botond\_Denes](https://sea2.discourse-cdn.com/flex016/user_avatar/forum.scylladb.com/botond_denes/32/163_2.png) [@Botond\_Denes](https://forum.scylladb.com/u/Botond_Denes)\
**Post date:** [November 22, 2024, 4:52am UTC](https://forum.scylladb.com/t/does-tombstone-blocks-shadowed-data-sstables-from-being-purged-in-twcs/3205/2 "2024-11-22T04:52:12Z")

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It is the other way around. SSTable B (the one with the shadowed data) will block the purge of SSTable A, in particular it will block the purge of the tombstone in SSTable A and said sstable can no longer be expired as a whole.