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So now we covered some interesting options for the write

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or for the insert operation and the write concern is also applicable to updates and deletes.

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Now there's one important concept I want to touch on and that is the atomicity of any write operation.

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Let's say we have an insert one operation but this could be any write operation again,

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now such operation

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most of the time will of course succeed but it can fail,

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there can be an error and here I'm talking about errors that happened whilst the document is inserted, so whilst

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it's written to memory, whilst it's handled by a storage engine.

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You could imagine that if you have a document with multiple fields, let's say also with a couple

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of embedded documents, that some of these fields end up in the database,

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so in the database files also whilst others are not included

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because in between,

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so whilst document was processed, the server had an issue.

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So if you added a person with name, age and hobbies, maybe name and age was saved but not hobbies, mongodb

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protects you against this,

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it guarantees you an atomic transaction which means the transaction either succeeds as a whole or it fails

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as a whole

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and if it fails during the write, everything is rolled back for this document you inserted

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and that is important.

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It's on a per document level, that document means the top level document,

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so it includes all embedded documents, all arrays so that is all included

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but if you use insert many with multiple documents being inserted, then you don't get this,

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so you only have support on a document level

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but if you have multiple documents in one operation, like insert many, then only each document on its

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own is guaranteed to either fail or succeed

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but not insert many.

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So if you have an issue during insert many, that just means that the documents on which it failed are

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not added

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and then the exact behavior depends on whether you used ordered or unordered inserts but the document

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which already were inserted will not be rolled back

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as I explained in the ordered and unordered insert lecture. We are actually able to control this on this

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bulk insert or bulk update level too

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and that will be related to a concept called transactions but that is something I will cover towards

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the end of this course because it requires some additional knowledge about mongodb and how the

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service work there that we don't have yet. But on a document level including all embedded documents, you

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have this atomic operation guarantee.