.. _es-guide-reference-index-modules-translog:

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Translog
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Each shard has a transaction log or write ahead log associated with it. It allows to guarantee that when an index/delete operation occurs, it is applied atomically, while not "committing" the internal lucene index for each request. A flush ("commit") still happens based on several parameters:


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 Setting                                  Description                                                                   
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index.translog.flush_threshold_ops       After how many operations to flush. Defaults to **5000**.                      
index.translog.flush_threshold_size      Once the translog hits this size, a flush will happen. Defaults to **500mb**.  
index.translog.flush_threshold_period    The period with no flush happening to force a flush. Defaults to **60m**.      
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