Are there always just 3 databases?

Question

I read this from the docs:

Sitecore CMS uses the following three SQL Server databases: Core – contains all settings, like a large configuration file for the Sitecore user interface. ... Master – contains all versions of all content. ... Web – contains the latest version of published content that has reached a final workflow state.

are there always just 3? or can there be more?

Answer 1

...can there be more?

One possible response is yes- to leverage a Preview Publishing Target. In this scenario you would duplicate your web database, connection string and definition. Rename to preview (for example).

Connection Strings

<add name="preview" connectionString="user id=sitecore;password=sitecore;Data Source=(local);Database=Sitecore_Preview" />

Definition

<?xml version="1.0"?>
<sitecore>
  <databases>
    <!-- preview -->
    <database id="preview" singleInstance="true" type="Sitecore.Data.DefaultDatabase, Sitecore.Kernel">
      <param desc="name">$(id)</param>
      <icon>Images/database_web.png</icon>
      <securityEnabled>true</securityEnabled>
      <dataProviders hint="list:AddDataProvider">
        <dataProvider ref="dataProviders/main" param1="$(id)">
          <disableGroup>publishing</disableGroup>
          <prefetch hint="raw:AddPrefetch">
            <sc.include file="/App_Config/Prefetch/Common.config" />
            <sc.include file="/App_Config/Prefetch/Webdb.config" />
          </prefetch>
        </dataProvider>
      </dataProviders>
      <proxiesEnabled>false</proxiesEnabled>
      <proxyDataProvider ref="proxyDataProviders/main" param1="$(id)" />
      <archives hint="raw:AddArchive">
        <archive name="archive" />
        <archive name="recyclebin" />
      </archives>
      <cacheSizes hint="setting">
        <data>100MB</data>
        <items>50MB</items>
        <paths>2500KB</paths>
        <itempaths>50MB</itempaths>
        <standardValues>2500KB</standardValues>
      </cacheSizes>
    </database>
  </databases>
</sitecore>

Workflow Considerations

With two web databases, you can leverage the Preview Publishing Target setting.

Publishing Target

Workflow State

This will promote items in this workflow state immediately to your preview target.

There are additional considerations with this configuration such as a separate CM and CD instances and indexing that fall outside the scope of your specific question. But, short answer, yes you can have additional databases.

Answer 2

Simplified version

For version 8, there are 4

• Core
  • Setting and Sitecore users
• Master
  • All versioned content for authors
• Web
  • All published content
• Reporting/Analytics
  • Aggregated analytics data from processing of xDB session data

For version 9, there are

• Core
  • Setting and Sitecore users
• EXM.Master
  • Email experience manager content
• ExperienceForms
  • Forms data from the new Sitecore 9 forms
• MarketingAutomation
  • All marketing automation rules and data.
• Master
  • All versioned content for authors
• Messaging
• Processing.Pools
• Processing.Tasks
• ReferenceData
• Reporting
  • Aggregated analytics data from processing of xDB session data
• Web
  • All published content

Answer 3

It depends on your version of Sitecore and if you are using xDB or WFFM or not but usually there are more than 3.

Here is an example of the DBs for an out of the box install of Sitecore 8:

If you are using xDB in Sitecore 8 then there is a reporting database in SQL Server too. There is also a Mongo DB Database to store the xDB data. If you are using Web Forms for Marketers (WFFM) there is a database to store the data for that module too (https://dev.sitecore.net/Downloads/Web_Forms_For_Marketers.aspx).

You can read more about Sitecore 8 xDB Architecture here:

https://doc.sitecore.net/sitecore_experience_platform/82/setting_up_and_maintaining/xdb/platform/architecture_overview

Here is an example of the DBs for an out of the box install of Sitecore 9:

In Sitecore 9 there are many more databases as in 9.0 and 9.0.1 Sitecore stores xDB data in SQL server instead of in MongoDB. This changed in 9.0.2 and above there is MongoDB support again, so there will be less databases if you choose to use MongoDB instead of SQL for xDB. Also it ships with an replacement for WFFM called Experience Forms so has a database for this.

You can read more about Sitecore 9 xDB Architecture here: https://doc.sitecore.net/developers/xp/index.html