# What is segments.terms\_memory\_in\_bytes? **URL:** \ **Category:** Elasticsearch\ **Created:** [December 10, 2016, 12:46pm UTC](https://discuss.elastic.co/t/what-is-segments-terms-memory-in-bytes/68621 "2016-12-10T12:46:12Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![WangXiangUSTC](https://avatars.discourse-cdn.com/v4/letter/w/8dc957/32.png) [@WangXiangUSTC](https://discuss.elastic.co/u/WangXiangUSTC)\ **Post date:** [December 10, 2016, 12:46pm UTC](https://discuss.elastic.co/t/what-is-segments-terms-memory-in-bytes/68621/1 "2016-12-10T12:46:12Z")
I use plugin head to monitor elasticsearch cluster, and I found that the segments.terms\_memory\_in\_bytes occupy most of the memory: "segments": { "count": 6813, "memory\_in\_bytes": 39858854460, "terms\_memory\_in\_bytes": 37379779192, "stored\_fields\_memory\_in\_bytes": 2461982384, "term\_vectors\_memory\_in\_bytes": 0, "norms\_memory\_in\_bytes": 6998592, "doc\_values\_memory\_in\_bytes": 10094292, "index\_writer\_memory\_in\_bytes": 16501940, "index\_writer\_max\_memory\_in\_bytes": 7467965004, "version\_map\_memory\_in\_bytes": 137381, "fixed\_bit\_set\_memory\_in\_bytes": 0 } what is it ? and how to reduce it? ---
**Author:** ![mikemccand](https://avatars.discourse-cdn.com/v4/letter/m/f04885/32.png) [@mikemccand](https://discuss.elastic.co/u/mikemccand)\ **Post date:** [December 10, 2016, 1:13pm UTC](https://discuss.elastic.co/t/what-is-segments-terms-memory-in-bytes/68621/2 "2016-12-10T13:13:15Z")
That's the heap memory Lucene uses to load the index into the terms dictionary and postings for indexed fields. It's a compact structure (a finite state transducer) so it's suprising yours are taking so much heap. Do you have many indexed fields? High cardinality indexed fields? Mike McCandless ---
**Author:** ![WangXiangUSTC](https://avatars.discourse-cdn.com/v4/letter/w/8dc957/32.png) [@WangXiangUSTC](https://discuss.elastic.co/u/WangXiangUSTC)\ **Post date:** [December 10, 2016, 3:35pm UTC](https://discuss.elastic.co/t/what-is-segments-terms-memory-in-bytes/68621/3 "2016-12-10T15:35:08Z")
yeah， At the first I use the default mapping, and every field will be indexed. can move some of them from heap by myself? ---
**Author:** ![mikemccand](https://avatars.discourse-cdn.com/v4/letter/m/f04885/32.png) [@mikemccand](https://discuss.elastic.co/u/mikemccand)\ **Post date:** [December 10, 2016, 9:56pm UTC](https://discuss.elastic.co/t/what-is-segments-terms-memory-in-bytes/68621/4 "2016-12-10T21:56:55Z")
The only way to do that is to stop indexing them. Mike McCandless ---
**Author:** ![WangXiangUSTC](https://avatars.discourse-cdn.com/v4/letter/w/8dc957/32.png) [@WangXiangUSTC](https://discuss.elastic.co/u/WangXiangUSTC)\ **Post date:** [December 12, 2016, 3:15am UTC](https://discuss.elastic.co/t/what-is-segments-terms-memory-in-bytes/68621/5 "2016-12-12T03:15:04Z")
new data will not insert into this index, and this index will be seldom searched. I delete some old data of this index, but the terms\_memory\_in\_bytes is not changed. Why ---
**Author:** ![mikemccand](https://avatars.discourse-cdn.com/v4/letter/m/f04885/32.png) [@mikemccand](https://discuss.elastic.co/u/mikemccand)\ **Post date:** [December 12, 2016, 1:03pm UTC](https://discuss.elastic.co/t/what-is-segments-terms-memory-in-bytes/68621/6 "2016-12-12T13:03:57Z")
To see a reduction in the terms heap usage, the segments containing the documents you deleted need to be merged away. If the indices really will no longer change, you could `forceMerge` them but this is a costly operation. Mike McCandless ---
**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\ **Post date:** [January 9, 2017, 1:04pm UTC](https://discuss.elastic.co/t/what-is-segments-terms-memory-in-bytes/68621/7 "2017-01-09T13:04:13Z")
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