{"id":4845,"date":"2015-05-21T12:39:53","date_gmt":"2015-05-21T10:39:53","guid":{"rendered":"https:\/\/www.dbi-services.com\/blog\/what-that-in-memory-term-is-about-and-what-not\/"},"modified":"2015-05-21T12:39:53","modified_gmt":"2015-05-21T10:39:53","slug":"what-that-in-memory-term-is-about-and-what-not","status":"publish","type":"post","link":"https:\/\/www.dbi-services.com\/blog\/what-that-in-memory-term-is-about-and-what-not\/","title":{"rendered":"What that in-memory term is about, and what not"},"content":{"rendered":"<p>Everybody is talking about in-memory databases these days. And everybody is talking about columnar store for sets of data because this can be a benefit for analytic queries. And a lot of people start mixing these terms not realizing that these topics are not exchangeable.<\/p>\n<p>Traditionally in-memory means: Not persistent, but fast. And this is what pure in-memory databases are: Not persistent, but fast, but, again: not persistent!!!<\/p>\n<p>They are just caching data for very fast access times. But: As soon as the in-memory database crashes or needs to be restarted the cache is gone and needs to be re-populated. So, how does this work together with relational databases like Oracle, MSSQL, PostgreSQL and all the others where persistence is one of the keys features they need to guarantee? The answer is: It does not. Yes, it does not. All of the relational databases are hybrids. Every database, and in fact every piece of software, needs to load data from disk into memory to access, modify and to save it. Nothing special about that. When it comes to relational databases all of them try to cache as much as possible in memory to get most performance for accessing and modifying the data. As soon as the data is modified it needs to be written to disk to guarantee the D in <a href=\"http:\/\/en.wikipedia.org\/wiki\/ACID\" target=\"_blank\" rel=\"noopener\">ACID<\/a>. No way around this: Data has to go to persistent storage. Most of the database vendors implement something like an <a href=\"https:\/\/en.wikipedia.org\/wiki\/Cache_algorithms#LRU\" target=\"_blank\" rel=\"noopener\">LRU<\/a> algorithm which keeps data that is accessed heavily in memory while data that is accessed less is getting dropped from memory and needs to be re-read from disk if someone wants to read and\/or modify it. The term in-memory as it is used currently is just a marketing term. Not more, not less. The &#8220;new&#8221; thing is just that memory is getting cheaper and cheaper and more and more data (even whole databases) can be cached today.<br \/>\nCoffee break reading: <a href=\"http:\/\/www.databasesoup.com\/2015\/02\/in-memory-is-not-feature-its-bug.html\" target=\"_blank\" rel=\"noopener\">&#8220;In-memory&#8221; is not a feature, it&#8217;s a bug <\/a><\/p>\n<p>Lets come to <a href=\"https:\/\/en.wikipedia.org\/wiki\/Column-oriented_DBMS\" target=\"_blank\" rel=\"noopener\">columnar storage<\/a> systems. The main goal of these is to avoid reading columns from disk that are not needed to satisfy a query and therefore to reduce I\/O. This is mainly beneficial for column oriented queries such as data warehouse queries. By storing the data in columnar format the system can skip reading the columns which are not needed to fulfill the request. In traditional row oriented storage systems the whole row must be read even if only few columns are requested. What has this to do with In-Memory? Nothing. Really nothing.<\/p>\n<p>Both, pure In-Memory databases and databases systems which store data in columnar format have their use cases. And there are more and more open source and commercial products which offer both. But: Try not to follow the marketing stuff and be aware of what it is really about.<br \/>\nIf you want to have more information on the topic and to meet our experts: <a title=\"boost your performances\" href=\"https:\/\/www.dbi-services.com\/newsroom\/events\/\">Event \u00ab In-Memory \u00bb: boost your IT performance!<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"<p>Everybody is talking about in-memory databases these days. And everybody is talking about columnar store for sets of data because this can be a benefit for analytic queries. And a lot of people start mixing these terms not realizing that these topics are not exchangeable. Traditionally in-memory means: Not persistent, but fast. And this is [&hellip;]<\/p>\n","protected":false},"author":29,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[198],"tags":[579,222],"type_dbi":[],"class_list":["post-4845","post","type-post","status-publish","format-standard","hentry","category-database-management","tag-column-store","tag-in-memory"],"acf":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO Premium plugin v27.2 (Yoast SEO v27.2) - https:\/\/yoast.com\/product\/yoast-seo-premium-wordpress\/ -->\n<title>What that in-memory term is about, and what not - dbi Blog<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.dbi-services.com\/blog\/what-that-in-memory-term-is-about-and-what-not\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"What that in-memory term is about, and what not\" \/>\n<meta property=\"og:description\" content=\"Everybody is talking about in-memory databases these days. And everybody is talking about columnar store for sets of data because this can be a benefit for analytic queries. And a lot of people start mixing these terms not realizing that these topics are not exchangeable. Traditionally in-memory means: Not persistent, but fast. 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He has more than 15 years of experience in management, engineering and optimization of databases and infrastructures, especially on Oracle and PostgreSQL. Since the beginning of his career, he has specialized in Oracle Technologies and is Oracle Certified Professional 12c and Oracle Certified Expert RAC\/GridInfra. Over time, Daniel has become increasingly interested in open source technologies, becoming \u201cTechnology Leader Open Infrastructure\u201d and PostgreSQL expert. \u00a0Based on community or EnterpriseDB tools, he develops and installs complex high available solutions with PostgreSQL. He is also a certified PostgreSQL Plus 9.0 Professional and a Postgres Advanced Server 9.4 Professional. He is a regular speaker at PostgreSQL conferences in Switzerland and Europe. Today Daniel is also supporting our customers on AWS services such as AWS RDS, database migrations into the cloud, EC2 and automated infrastructure management with AWS SSM (System Manager). He is a certified AWS Solutions Architect Professional. Prior to dbi services, Daniel was Management System Engineer at LC SYSTEMS-Engineering AG in Basel. Before that, he worked as Oracle Developper &amp;\u00a0Project Manager at Delta Energy Solutions AG in Basel (today Powel AG). Daniel holds a diploma in Business Informatics (DHBW, Germany). His branch-related experience mainly covers the pharma industry, the financial sector, energy, lottery and telecommunications.\",\"sameAs\":[\"https:\/\/x.com\/westermanndanie\"],\"url\":\"https:\/\/www.dbi-services.com\/blog\/author\/daniel-westermann\/\"}]}<\/script>\n<!-- \/ Yoast SEO Premium plugin. -->","yoast_head_json":{"title":"What that in-memory term is about, and what not - dbi Blog","robots":{"index":"index","follow":"follow","max-snippet":"max-snippet:-1","max-image-preview":"max-image-preview:large","max-video-preview":"max-video-preview:-1"},"canonical":"https:\/\/www.dbi-services.com\/blog\/what-that-in-memory-term-is-about-and-what-not\/","og_locale":"en_US","og_type":"article","og_title":"What that in-memory term is about, and what not","og_description":"Everybody is talking about in-memory databases these days. And everybody is talking about columnar store for sets of data because this can be a benefit for analytic queries. 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He is a certified AWS Solutions Architect Professional. Prior to dbi services, Daniel was Management System Engineer at LC SYSTEMS-Engineering AG in Basel. Before that, he worked as Oracle Developper &amp;\u00a0Project Manager at Delta Energy Solutions AG in Basel (today Powel AG). Daniel holds a diploma in Business Informatics (DHBW, Germany). 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