Thanks Alain/Chris. Firstly I am not seeing any difference when using gc_grace_seconds with sstablemetadata.
CREATE TABLE ks.nmtest ( reservation_id text, order_id text, c1 int, order_details map<text, text>, PRIMARY KEY (reservation_id, order_id) ) WITH CLUSTERING ORDER BY (order_id ASC) AND bloom_filter_fp_chance = 0.01 AND caching = {'keys': 'ALL', 'rows_per_partition': 'NONE'} AND comment = '' AND compaction = {'class': 'org.apache.cassandra.db.compaction.SizeTieredCompactionStrategy', 'max_threshold': '32', 'min_threshold': '4'} AND compression = {'chunk_length_in_kb': '64', 'class': 'org.apache.cassandra.io.compress.LZ4Compressor'} AND crc_check_chance = 1.0 AND dclocal_read_repair_chance = 0.1 AND default_time_to_live = 0 AND gc_grace_seconds = 86400 AND max_index_interval = 2048 AND memtable_flush_period_in_ms = 0 AND min_index_interval = 128 AND read_repair_chance = 0.0 AND speculative_retry = '99PERCENTILE'; [root@ip-xxx-xxx-xxx-xxx nmtest-e1302500201d11e983bb693c02c04c62]# sstabledump mc-11-big-Data.db WARN 08:27:32,793 memtable_cleanup_threshold has been deprecated and should be removed from cassandra.yaml [ { "partition" : { "key" : [ "4" ], "position" : 0 }, "rows" : [ { "type" : "row", "position" : 40, "clustering" : [ "4" ], "cells" : [ { "name" : "order_details", "path" : [ "key1" ], "value" : "value1", "tstamp" : "2019-01-27T08:26:49.633240Z" } ] } ] }, { "partition" : { "key" : [ "5" ], "position" : 41 }, "rows" : [ { "type" : "row", "position" : 82, "clustering" : [ "5" ], "liveness_info" : { "tstamp" : "2019-01-27T08:23:29.782506Z" }, "cells" : [ { "name" : "c1", "value" : 5 }, { "name" : "order_details", "deletion_info" : { "marked_deleted" : "2019-01-27T08:23:29.782505Z", "local_delete_time" : "2019-01-27T08:23:29Z" } }, { "name" : "order_details", "path" : [ "key" ], "value" : "value" } ] } ] } Partition 5 is a newly inserted record, no matter what gc_grace_seconds value I pass it still shows this record as estimated tombstone. [root@ip-xxx-xxx-xxx-xxx nmtest-e1302500201d11e983bb693c02c04c62]# sstablemetadata mc-11-big-Data.db | grep "Estimated tombstone drop times" -A3 Estimated tombstone drop times: 1548577440: 1 Count Row Size Cell Count [root@ip-xxx-xxx-xxx-xxx nmtest-e1302500201d11e983bb693c02c04c62]# sstablemetadata --gc_grace_seconds 86400 mc-11-big-Data.db | grep "Estimated tombstone drop times" -A4 Estimated tombstone drop times: 1548577440: 1 Count Row Size Cell Count Second question, for this test table I see the original record which I inserted got its tombstone removed by autocompaction which ran today as its gc_grace_seconds is set to one day. But I see some tables whose gc_grace_seconds is set to 3 days but when I do sstabledump on them I see tombstone entries for them in the json output and sstablemetadata also shows them to be estimated tombstones records. I see autocompaction is running on the stables of this table and I also manually ran using jmx shell but they are still there...any reason why they are not getting deleted? sstablemetadata --gc_grace_seconds 259200 mc-732-big-Data.db | grep "Estimated tombstone drop times" -A10 WARN 07:28:03,086 memtable_cleanup_threshold has been deprecated and should be removed from cassandra.yaml Estimated tombstone drop times: 1537475340: 7 1537476150: 14 1537476360: 7 1537476660: 7 one record from son file having old tombstone markers.... { "partition" : { "key" : [ "2945132807" ], "position" : 9036596 }, "rows" : [ { "type" : "row", "position" : 9037781, "clustering" : [ "2018-08-15 00:00:00.000Z", "233359" ], "liveness_info" : { "tstamp" : "2018-09-26T14:52:54.255395Z" }, "cells" : [ ..... { "name" : "col1", "deletion_info" : { "marked_deleted" : "2018-09-26T14:52:54.255394Z", "local_delete_time" : "2018-09-26T14:52:54Z" } }, { "name" : "col1", "path" : [ "zczxc" ], "value" : "ZXczx" }, { "name" : "col1", "path" : [ "ZXCxzc" ], "value" : "ZCzxc" }, { "name" : "col2", "deletion_info" : { "marked_deleted" : "2018-09-26T14:52:54.255394Z", "local_delete_time" : "2018-09-26T14:52:54Z" } }, { "name" : "col2", "path" : [ "zcxxc" ], "value" : false }, { "name" : "col2", "path" : [ "hjhkjh" ], "value" : false }, { "name" : "col2", "path" : [ "LEGACY" ], "value" : true }, { "name" : "col2", "path" : [ "NON_SITE_SPECIFIC" ], "value" : true }, { "name" : "issuance_data", "deletion_info" : { "marked_deleted" : "2018-09-26T14:52:54.255394Z", "local_delete_time" : "2018-09-26T14:52:54Z" } }, .....