# Open an Index- core operations **URL:** \ **Category:** Elastic Training\ **Created:** [September 12, 2017, 8:35am UTC](https://discuss.elastic.co/t/open-an-index-core-operations/100172 "2017-09-12T08:35:30Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![SKumarMN](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/skumarmn/32/27537_2.png) [@SKumarMN](https://discuss.elastic.co/u/SKumarMN)\ **Post date:** [September 12, 2017, 8:35am UTC](https://discuss.elastic.co/t/open-an-index-core-operations/100172/1 "2017-09-12T08:35:30Z")
As part of core operations course materials, I see a slide for "Open an Index" with below content Be aware that opening an index can take a few seconds or even a couple of minutes -The primary shards may need some updates applied ‒ A Lucene index will be opened (can take time), and the transaction log will be replayed I have few questions: When we reopen an index, in what scenarios will the primary gets updated( or may need updates) . When we close an index since we would have done synced flush, why will it replay from transaction logs or even if i dont do sysnced flush before closing an index, wouldn't ES flush everything from translog bfr closing an index? ---
**Author:** ![abdon](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/abdon/32/9195_2.png) [@abdon](https://discuss.elastic.co/u/abdon)\ **Post date:** [September 12, 2017, 12:03pm UTC](https://discuss.elastic.co/t/open-an-index-core-operations/100172/2 "2017-09-12T12:03:21Z")
You are right: when you close an index we do advise you to do a synced flush. It's not mandatory though, and that's what this slide warns you about. When you close an index without doing a synced flush, it's not unlikely that the translog will have to be replayed for that index when you reopen it. Those transactions in the translog are the updates to the primary shards that this slide mentions. ---
**Author:** ![SKumarMN](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/skumarmn/32/27537_2.png) [@SKumarMN](https://discuss.elastic.co/u/SKumarMN)\ **Post date:** [September 13, 2017, 10:03am UTC](https://discuss.elastic.co/t/open-an-index-core-operations/100172/3 "2017-09-13T10:03:48Z")
Thanks for your reply ---
**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\ **Post date:** [October 13, 2017, 10:04am UTC](https://discuss.elastic.co/t/open-an-index-core-operations/100172/4 "2017-10-13T10:04:00Z")
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