SharePoint Interview Q&A

Thought to Share To help Other SharePoint Bees, who is learning SharePoint And Preparing for Interview for SharePoint Position.

Good Luck & All the very Best!!!!!!!!!!!!!!                          

sharepoint online migration interview Q&A or sharepoint migration sharegate interview questions:

1. How the users were Mapped?
2. is infopath available in SPO? 
3. what are the common issues & difficulties which you got during Migration?
4. How to migrate  the Term stores migrated to SPO?
5. How to create info path forms on SPO?
6. How to create Apps in SPO?
7. How to map users in SPO?
8. How to connect SPO site to other sources?
9. What is the role of security group in Azure?
10. what is online Governence?
11. How many stages the Migration can be done?
12. what is Delta or Incremental Migration?
13. what is the use of SPMT tool?
14. what is the best Migration tool?
15. did you has any experiance in ShareGate Migration tool?
16. what is Normal mode and Insane mode in Sharegate?
17. what are the limitations of ShareGate Migation tool?
18. what are the Scripts used in Sharepoint Migration?
19. what are the Important commands used for Migration?
20. what is PNPPowershell?

SharePoint 2013 Q&A

1) What are the three user authentication methods that SharePoint 2013 supports?

1. Windows claims
2. Security Assertion Markup Language (SAML)-based claims
3. Forms-based authentication claims

2) Out of the available authentication methods, which one would is considered the recommend according to Microsoft?

Claims-based authentication methods are recommended.

3) What protocol does server-to-server authentication extend?

SharePoint 2013 extends OAuth.

4) SharePoint Store and App Catalog Access SharePoint resources on behalf of a user using?

OAuth 2.0.

5) What Business Data Connectivity (BDC) connections types are supported in SharePoint 2013?

1. WCF
2. SQL Server
3. NET assemblies
4. Open Data Protocol

6) What are some examples of technology that OData leverages?

1. HTTP
2. Atom Publishing Protocol (AtomPub)
3.  JavaScript Object Notation (JSON)

7) What types of authentication does Business Connectivity Services support?

1. Anonymous
2. Basic
3. Windows
4. Custom authentication to OData services when it is used with the Secure Store Service

8) What does a BDC model do?

Describes which tables to read, which items from those tables are of interest, and which operations to perform on them.

9) How is the BDC model in SharePoint 2013 more streamlined than in SharePoint 2010?

Visual Studio 2010 is able to connect to the OData endpoint through Business Connectivity Services and read the OData source. Visual Studio 2010 will then automatically generate the BDC model.

10) How is the BDC model used after being built?

Imported into the Business Data Catalog as a farm-scoped external content type, or be included in an app for SharePoint.

11) What Is An Event Listener in SharePoint 2013?

The event listener includes an event subscriber. The subscriber receives notifications from the event publisher (on the external system side) on changes to the data and then initiates predefined actions when changes occur.

12) How is an event listener useful?

Enables SharePoint users and custom code to receive notifications of events that occur in an external system.

13) With an event listener, what are the supported connections for an external system?

1. OData
2. SQL
3. WCF

14) What are apps for SharePoint?

Apps for SharePoint allow addition of functionality to a SharePoint site by using the self-contained app for SharePoint.

15) What is the primary benefit of using apps for SharePoint?

Each app for SharePoint is isolated from the rest of the system.

16) How are BDC models and apps for SharePoint related?

BDC models can be scoped to apps for SharePoint and connection information is defined and stored separately from the app-scoped BDC model in BDC connections.

17) What is eDiscovery in the context of SharePoint 2013?

Introduces a new site for managing discovery cases and holds. The site allows one to access discovery cases to conduct searches, place content on hold, and export content.

18) What are some examples of some things you can related to an eDiscovery case?

1. Sources
2. eDiscovery sets
3. Queries
4. Exports

 19) What is an in-place hold?

Content that is put on hold is preserved, but users can still change it.

20)  What the content can be included with SharePoint eDiscovery export?

1. Document
2. Lists
3. Pages
4. Exchange objects

21) In terms of enterprise-wide eDiscovery, what actions can be taken by an authorized user?

1.  Create a case, define a query, and then search SharePoint Server 2013, Exchange Server 2013, and file shares
2. Export all of the content that was identified.
3. Preserve items in place in SharePoint Server 2013 or Exchange Server 2013.
4. Track statistics related to the case.

22) What are the different types of mobile views offered in SharePoint 2013?

1. Contemporary view
2. Classic view
3. Full screen UI

23) What is the Microsoft Push Notification Service?

Supports applications on mobile devices that should receive notifications from a SharePoint site.

24) What field type would be used when working location specific SharePoint applications?

Geolocation field type

25) What is Site-based retention?

You can create and manage retention policies in that will apply to SharePoint sites and any Exchange Server 2013 team mailboxes that are associated with the sites.

26) What does a retention policy contain?

Generally what causes a project to be closed and when a project should expire.

27) What are some improvements in Excel Services in SharePoint 2013?

1. Field list and field well support
2. Calculated measures and members
3. Enhanced timeline controls
4. Application BI Servers
5. Business Intelligence Center update

 28) What is the In-Memory BI Engine (IMBI)?

The In Memory multidimensional data analysis engine (IMBI), also known as the Vertipaq engine, allows for almost instant analysis.

29) What does the Power View Add-in for Excel do?

Power View (“Crescent”) enables users to visualize and interact with modeled data by using highly interactive visualizations, animations and smart querying.

30) Can PerformancePoint be displayed on iPads?

Yes.

31) What is the Analysis Services Effective User?

Eliminates the need for Kerberos delegation when per-user authentication is used for Analysis Services data sources. By supporting Analysis Services Effective User feature, authorization checks will be based on the user specified by the EffectiveUserName property instead of using the currently authenticated user.

32) What are Community Sites in SharePoint 2013?

Community Sites offer a forum experience to categorize and cultivate discussions with a broad group of people across organizations in a company.

33) What is the primary change with MySite document libraries in 2013?

Users can specify permissions for a specific document without having to understand the inheritance model.

34) What are Image renditions?

Image renditions let you display different sized versions of an image on different pages.

35) How are multilingual sites implemented?

Variations, integrated translation service, cross-site publishing

36)  What is Cross-site publishing?

Cross-site publishing lets you store and maintain content in one or more authoring site collections, and display this content in one or more publishing site collections.

37) What is Managed navigation?

Managed navigation lets you define and maintain the navigation on a site by using term sets.

38) What are Category pages?

Category pages are page layouts that are used for displaying structured content such as catalog data.

39)  What is the Content Search Web Part?

Displays content that was crawled and added to the search index.

40) What are Refiners and faceted navigation?

Refiners are based on managed properties from the search index. With faceted navigation you can configure different refiners for different terms in a term set.

41) What is the Analytics Processing Component?

Runs different analytics jobs to analyze content in the search index and user actions that were performed on a site to identify items that users perceive as more relevant than others.

42) What does the Workflow Manager do?

High Density and Multi-Tenancy, Elastic Scale, Activity / Workflow Artifact Management, Tracking and Monitoring, Instance Management, Fully Declarative Authoring, REST and Service Bus Messaging, Managed Service Reliability.

43) What is a ranking model in SharePoint 2013 search?

A ranking model determines recall (which items are displayed in the search results) and rank (the order in which search results are displayed).

44) What actions can a query rule specify?

1. Add one or more result blocks
2. Change ranked results
3. Add Promoted Results (formerly called Best Bets) that appear above ranked results

45) What are Result sources?

Result source allow you to restrict queries to a subset of content by using a query transform.

 46) What is a Continuous crawl?

Eliminates the need to schedule incremental crawls and automatically starts crawls as necessary to keep the search index fresh.

47) How can you remove items from the search index?

Using the crawl logs.

48) How can you specify which entities to look for in the content in relation to SharePoint search?

Create and deploy your own dictionaries

49) What does document parsing functionality do?

Document parsers extract useful metadata and remove redundant information.

50) Is Visual Upgrade available in SharePoint 2013?

No.

51) What are the New Changes in Search?
In SharePoint 2013 the best of two Search Engines "SharePoint Search" and “FAST Search Server for SharePoint” was combined
to make one Search Engine that would provide greater redundancy and for better scalability. For more Info on Search architecture see Search 2013 Architecture

Q2. What is Continuous Crawl?
Ans: A new Crawl Option "Continuous crawls" has been Introduced in search's Crawl Schedule Category to help keep the search index and search results as fresh as possible. Continuous crawls run every 15 minutes by default.

Q3. What are Display Templates?
Ans: To eliminate the fact that the designers and power users needed to modify the XSLT each time they needed a particular look and feel in SharePoint, a new concept of Design Templates has been introduced. Each Display Template consist of two files an HTML file (.html) and JavaScript File (.js). For more Info on Display templates see Display Templates

Q4. What is the new Analytics Processing Component in SharePoint 2013?
Ans: The Analytics Processing Component in SharePoint Server 2013 analyzes both the Content and the way users interact with it.The results from the analysis are added to the items in the search index to be used by Search Webparts,Recommendation Reports,Most Popular Items reports and other WebParts.

Q5: What analysis are done by Analytics Processing Component in SharePoint 2013?
Ans: The Analytics Processing Component runs two main types of analyses: Search analytics and Usage analytics. Search analytics analyzes content in the search index, and usage analytics analyzes the user actions.

Q6. What is the purpose of new Content Search Web Part(CSWP)?
Ans: In SharePoint 2013 Microsoft has introduced a new webpart called “Content Search Web Part (CSWP)”.This Web Part queries
against search Index to display results. The webpart displays search results in a way that you can easily format it and customize it.

Q7. What is Shredded Storage?
Ans: It’s a new Feature Introduced in SharePoint 2013 where Documents and Changes to the Documents are stored as “Shredded BLOBS” in the new DocStreams Data Table. Unlike SharePoint 2010, it helps to lower down the amount of storage required for saving files by saving only the Changes and not the entire Versions of the Files in database.

Q8: Why would you Disable Shredded Storage?
Ans: Shredded storage is a per document feature.So if two Copies of the exactly same document is stored in two different libraries, these two documents will still have their own set of shreds which will take up twice the space of each individual document.

Q9. Whats new in SPSite Powershell Cmdlet?
Ans: SPSite has few new parameters in SharePoint 2013 to make Site Collection Operations easier.
New-SPSite cmdlet allows to Create a Host-name Site Collections adding a using the HostHeaderWebApplication parameter that identifies the Web Application where the site collection is being Created.
Copy-SPSite (new) Use the Copy-SPSite cmdlet to make a copy of a site collection from one Source content database to a specified destination content database.The copy of the site collection has a new URL and a new SiteID.This will be very useful when renaming a SiteCollection.


Q10: Whats are the new Delegate Controls in SharePoint 2013?
Ans: In SharePoint 2013, three New Delegate Controls have been Introduced for the purpose of displaying the new Top Suite bar (with links SkyDrive, NewsFeed,Sync,follow). These Controls are -

• SuiteBarBrandingDelegate delegate Control
• SuiteLinksDelegate delegate Control
• PromotedActions Delegate Control

Q11: What are the Changes in CSOM and REST based APIs?
Ans:  Microsoft has improved both Client Side Object Model (CSOM) and Representational State Transfer (REST) based APIs by adding a much needed support for the Search, User Profiles, Taxonomies, and Publishing Object Model.Client.svc service is extended with REST capabilities and accepts HTTP GET, PUT, POST requests.


Q12: What’s the new App model?
Ans: SharePoint 2013 Introduces a Cloud App Model that enables you to Create apps.Apps for SharePoint are self-contained pieces of functionality that extend the capabilities of a SharePoint website. An app may include SharePoint components such as lists, workflows, and site pages, but it can also surface a remote web application and remote data in SharePoint.

Q13: What is the new SPSecurityEventReceiver?
Ans:  SharePoint 2013 Introduces a Cloud App Model that enables you to Create apps.Apps for SharePoint are self-contained pieces of functionality that extend the capabilities of a SharePoint website. An app may include SharePoint components such as lists, workflows, and site pages, but it can also surface a remote web application and remote data in SharePoint.

SharePoint 2010 Q&A

What is SharePoint? 

 SharePoint is a portal collaboration software, SharePoint 2010 is a platform where user can share Data, Collaborate and people can also take this platform and customized platform as per their requirements.

 What are the types of authentication available for SharePoint 2010?

1. Claims

2. Windows(classic)

3. Form Based Authentication

What are the two different versions in SharePoint 2010?

SharePoint 2010 has 2 different products namely SharePoint Foundation 2010 and SharePoint Server 2010.

SharePoint Foundation 2010

SharePoint Server 2010

What’s new in Shared Service Provider (SSP) in SharePoint 2010 ?

“Service Application “or “Service App” is a concept in SharePoint 2010, where SSP Services are split out into separate services.

Profiles, Audiences People Service Application

Search Service Application

Excel Service Application

Project Server Application

Visio service application

What is the GAC?

The GAC stands for the global assembly cache. It is the machine wide code cache which will give custom binaries place into the full trust code group for SharePoint. Certain SharePoint assets, such as Feature Receivers need full trust to run correctly, and therefore are put into the GAC.

C:\WINDOWS\assembly) or %WINDIR%\Microsoft.NET\assembly

What is a site collection?

A site collection contains a top-level website and can contain one or more sub-sites web sites that have the same owner and share administration settings.

What are Web Application Policies?

Enables security policy for users at the Web application level, rather than at the site collection or site level. Importantly, they override all other security settings.

What are content databases?

A content database can hold all the content for one or more site collections.

What is the difference between Classic mode authentication and Claims-based authentication?

As the name implies, classic authentication supports NT authentication types like Kerberos, NTLM, Basic, Digest, and anonymous. Claims based authentication uses claims identities against a trusted identity provider.

When would you use claims, and when would you use classic?

Classic is more commonly seen in upgraded 2007 environments whereas claims are the recommended path for new deployments.

What are Terms and Term Sets?

A term is a word or a phrase that can be associated with an item. A term set is a collection of related terms.

What are different types of Term Sets?

There are Local Term Sets and Global Term Sets, one created within the context of a site collection and the other created outside the context of a site collection, respectively.

What Is Governance in terms of SharePoint 2010?

Governance is the set of policies, roles, responsibilities, and processes that guide, direct, and control how an organization’s business divisions and IT teams cooperate to achieve business goals.

What are some useful, OOB features of SharePoint that aid with governance of an environment?

Please refer the following options:

Site templates – consistent branding, site structure, and layout can be enforce a set of customizations that are applied to a site definition.

Quotas – limits to the amount of storage a site collection can use.

Locks - prevent users from either adding content to a site collection or using the site collection.

Web application permissions and policies – comprehensive security settings that apply to all users and groups for all site collections within a Web application.

Self-service site creation - enables users to create their own site collections, thus must be incorporated into a governance scheme.

Basic Intro SharePoint Architecture Questions :

 What are Web Applications in SharePoint?

An IIS Web site created and used by SharePoint 2010. Saying an IIS virtual server is also an acceptable answer.

What is an application pool?

A group of one or more URLs that are served by a particular worker process or set of worker processes. Allows us to configure a level of isolation between diff web applications.

 Why are application pools important?

They provide a way for multiple sites to run on the same server but still have their own worker processes and identity.

What are zones?

Different logical paths (URLs meaning) of gaining access to the same SharePoint Web application.

What is a site?

 A site in SharePoint contains Web pages and related assets such as lists, all hosted within a site collection.

What are My Sites?

Specialized SharePoint sites personalized and targeted for each user.

 Describe the potential components for both a single server, and multiple servers, potentially several tiered farms:

A single-server SharePoint Server 2010 environment leverages a built-in SQL Server 2008 Express database. The problems with this environment is scalability, not being able to install the with built-in database on a domain controller, the database cannot be larger than 4 GB, and you cannot use User Profile Synchronization in a single server with built-in database installation.

An example of a multiple tier farm would be a three-tier topology, considered one of the more efficient physical and logical layouts to supports scaling out or scaling up and provides better distribution of services across the member servers of the farm. This is considered a good architecture since one can add Web servers to the Web tier, add app servers to the application tier, and add database servers to the database tier.

SharePoint Backup and Restore Questions:

 What are some of the tools that can be used when backing up a SharePoint 2010 environment?

• SharePoint farm backup and recovery
• SQL Server
• System Center Data Protection Manager

 What Microsoft tool can be used for incremental backups?

System Center Data Protection Manager

Managed Metadata Questions:

 What is Managed Metadata?

Managed metadata is a hierarchical collection of centrally managed terms that you can define, and then use as attributes for items.

 What are Terms and Term Sets?

A term is a word or a phrase that can be associated with an item.  A term set is a collection of related terms.

 How do Terms and Term Sets relate to Managed Metadata?

Managed metadata is a way of referring to the fact that terms and term sets can be created and managed independently from the columns themselves.

Are there different types of Term Sets?

There are Local Term Sets and Global Term Sets, one created within the context of a site collection and the other created outside the context of a site collection, respectively.

How are terms created and used?

There are several ways; however the most common is to use the Term Store Management Tool.

How are Managed Metadata, and the related Term technology used?

Through the UI, the most common use is through the managed metadata list column which allows you to specify the term set to use. It also related to searching and enhancing the user search experience.

Sandbox Solutions Questions:

 What is a sandboxed solution?

Components that are deployed to run within the sandboxed process rather than running in the production Internet Information Services (IIS) worker process.

 What are some examples of things that might run within the SharePoint sandbox?

Any of the following are acceptable answers:

 Web Parts
Event receivers
Feature receivers
Custom Microsoft SharePoint Designer workflow activities
Microsoft InfoPath business logic

Others….

Why are sandboxed solutions used?

Primarily because they promote high layers of isolation. By default they run within a rights-restricted, isolated process based around Code Access Security (CAS). Isolation is possible to increase with activities like running the sandboxing service on only specific SharePoint 2010 servers.

SharePoint Search Questions:

What is a content source in relation to SharePoint search? What’s the minimum amount of content sources?

A content source is a set of options that you can use to specify what type of content is crawled, what URLs to crawl, and how deep and when to crawl. You must create at least one content source before a crawl can occur.

What is a search scope?

A search scope defines a subset of information in the search index. Users can select a search scope when performing a search.

What is a federated location with SharePoint search?

Federated locations provide information that exists outside of your internal network to your end-users.

How does managed metadata affect search?

Enhances the end-user search experience by mapping crawled properties to managed properties. Managed properties show up in search results and help users perform more successful queries.

What is query logging in SharePoint 2010?

Collects information about user search queries and search results that users select on their computers to improve the relevancy of search results and to improve query suggestions.

What authentication type does the SharePoint crawler use?

The crawl component requires access to content using NTLM authentication.

Services Architecture Questions:

Please describe what a Service Application is in SharePoint 2010.

Service applications in SharePoint 2010 are a set of services that can possibly be shared across Web applications. Some of these services may or may not be shared across the SharePoint 2010 farm. The reason these applications are shared is the overall reduction of resources required to supply the functionality these services cultivate.

Please provide an example of one of these service applications.

Any of the below are acceptable answers:

Access Services
Business Data Connectivity service
Excel Services Application
Managed Metadata service
Performance Point Service Application
Search service
Secure Store Service
State service
Usage and Health Data Collection service
User Profile service
Visio Graphics Service
Web Analytics service
Word Automation Services
Microsoft SharePoint Foundation Subscription Settings Service

 What are Service Application Groups used for?

Just provides a logical grouping of services that are scoped to a particular Web Application.

How are Service Applications deployed in terms of IIS (Internet Information Services)?

They are provisioned as a single Internet Information Services (IIS) Web site.

Explain how connections are managed with Service Applications.

A virtual entity is used that is referred to as a proxy, due to label in Power Shell.

What are some common examples of SharePoint 2010 services architectures, and what are the advantages of each design?

The three most popular designs are single farms with either a single service application group or multiple service application groups, or Enterprise services farms.

Single farms with a single service application group are generally the most common, and have the advantages of easy deployment, simple service application allocation, effective resource utilization and cohesive management.

Single farms with multiple service application groups is less common, and have the advantage of potential individual management of service applications as well as allowing data isolation, and while being more complex to deploy and maintain allows targeting of sites to particular service applications.

Enterprise Service Farms is pretty uncommon as it is a complete farm dedicated to Service Applications but promotes autonomous management and high levels of data isolation.

Are there any other type of relevant service architectures?

Depending on the environment requirements, a specialized farm can also be used in order to deploy specific services tailored to the organizational requirements which can aid in scaling out and conservation of resources.

What is the User Profile service?

Allows configuring and managing User profile properties, Audiences, Profile synchronization settings, organization browsing and management settings, and My Site settings.

 What are User Profiles?

Aggregates properties from diverse identity content sources together to create unified and consistent profiles across an organization, used throughout the SharePoint environment.

What is Excel Services?

Allows sharing, securing, managing, and using Excel 2010 workbooks in a SharePoint Server Web site or document library. Excel Services consists of the Excel Calculation Services (ECS), Microsoft Excel Web Access (EWA), and Excel Web Services (EWS) components.

What is Performance Point Services?

Allows users to monitor and analyze a business by building dashboards, scorecards, and key performance indicators (KPIs).

What is Visio Services?

Allows users to share and view Microsoft Visio Web drawings. The service also enables data-connected Microsoft Visio 2010 Web drawings to be refreshed and updated from various data sources.

What is Access Services?

Allows users to edit, update, and create linked Microsoft Access 2010 databases that can be viewed and manipulated by using an internet browser, the Access client, or a linked HTML page.

What is the Secure Store Service (SSS)?

A secure database for storing credentials that is associated with application IDs

What is Content Deployment?

Content deployment enables you to copy content from a source site collection to a destination site collection.

Backup / DR Questions:

 Describe how redundancy can be built into a SharePoint environment. Please be specific in regards to any auxiliary components.

Multiple front-end web servers (WFE’s) can be deployed and correlated through Windows NLB or anything approach. Application servers can be deployed into the farm for a variety of purposes, depending on organizational requirements. Databases can be clustered or mirrored, again depending on requirements and environment.

From a basic standpoint, what is the difference between SQL clustering and mirroring?

Clustering provides a failover scenario whereby one or more nodes can be swapped as active depending on whether a node goes down. In mirroring, transactions are sent directly from a principal database and server to a mirror database to establish essentially a replica of the database.

Governance Questions:

What Is Governance in terms of SharePoint 2010?

Governance is the set of policies, roles, responsibilities, and processes that guide, direct, and control how an organization’s business divisions and IT teams cooperate to achieve business goals.

 What are some useful, OOB features of SharePoint that aid with governance of an environment?

Any of the below are acceptable answers. There are some others but these are the major ones that I generally look for from a candidate:

Site templates – consistent branding, site structure, and layout can be enforce a set of customizations that are applied to a site definition.

Quotas – limits to the amount of storage a site collection can use.

Locks - prevent users from either adding content to a site collection or using the site collection.

Web application permissions and policies – comprehensive security settings that apply to all users and groups for all site collections within a Web application.

Self-service site creation - enables users to create their own site collections, thus must be incorporated into a governance scheme.

Monitoring Questions:

Describe the monitoring features that are baked into SharePoint 2010.

Diagnostic logging captures data about the state of the system, whereas health and usage data collection uses specific timer jobs to perform monitoring tasks, collecting information about:

• Performance Counter Fata
• Event Log Data
• Timer Service Data
• Metrics For Site Collections and Sites
• Search Usage Data 

what’s the service application proxy?

Essentially, the service application proxy is a virtual link that connects web applications to a particular service application. So, when you create your web application, you can specify your association to a service-application proxy, and it’s the proxy that actually manages the communication back and forth.

BloB Cache Questions:

1.What is Blob Cache?

Disk-based Caching for Binary Large Objects

Disk-based caching controls caching for binary large objects (BLOBs) such as image, sound, and video files, as well as code fragments. Disk-based caching is extremely fast and eliminates the need for database round trips. BLOBs are retrieved from the database once and stored on the Web client. Further requests are served from the cache and trimmed based on security.

2.Enabling and modifying disk-based caching for SharePoint sites.

Disk-based caching is disabled by default. To enable and customize the disk-based cache, you must modify the following statement in the web.config file for the SharePoint Web application.

By default, it looks like this:
<BlobCache location="C:\blobCache" path="\.(gif|jpg|png|css|js)$" maxSize="10" enabled="false" />

In order to improve the performance of your site, the BlobCache should be enabled.
<BlobCache location="C:\blobCache" path="\.(gif|jpg|png|css|js)$" maxSize="10" enabled="true" />

Example:

<BlobCache location="C:\blobCache" path="\.(gif|jpg|png|css|js)$" maxSize="10" max-age="86400" enabled="false"/>

In the preceding example:

• location is the directory where the cached files will be stored
• path specifies in the form of a regular expression which files are cached based on the file extension
• maxSize is the maximum allowable size of the disk-based cache in gigabytes
• max-age specifies the maximum amount of time in seconds that the client browser caches BLOBs downloaded to the client computer. If the downloaded items have not expired since the last download, the same items are not re-requested when the page is requested. The max-age attribute is set by default to 86400 seconds (that is, 24 hours), but it can be set to a time period of 0 or greater.
• enabled is a Boolean that disables or enables the cache.

3. Flushing the Disk-based Cache:

We can flush the current site collection object cache. To do this, browse to the following location on the web site,
Site collection administration -> site collection object cache -> disk based cache reset.

If we have multiple WFEs in the farm, each WFE will maintain its own copy of Disk-based Cache. SharePoint does not have a Web user interface (UI) to flush the disk-based cache on all the servers in a farm and neither is there an option to select a specific WFE.

4.The option provided in the Administration page for flushing the cache is only to the flush the cache on the web front end to which you are currently browsing.

if you would like to flush the complete binary large object (BLOB) caches associated with a specific Web Application on different Web front-end computers in a farm, then you can use the STSADM command to do so.

STSADM -o setproperty -propertyname blobcacheflushcount -propertyvalue 11 -url http://mywebapp:port

5.Internals of the blob cache functionality within SharePoint:

After enabling blob cache in web.config, do an IISRESET and browse to the /settings.aspx first, instead of home page (Collaboration portal site).

When we browse to the settings.aspx, it will create the following files change.bin, dump.bin and flushcount.bin (all the files will be 1KB in size).

Browse to the home page now, it will create a folder PUBLISHINGIMAGES, all the images rendered from the database will be stored here and the above bin files will also get updated (we can see the difference in file size).

Every time when a new image file is rendered from the database, the image folder gets a copy of the image. The bin files (index) will get updated with an additional entry for the new file.

Every request from client will check the index file first. It will only check the cache index and not the image folder directly for the image. If the index file does not have an entry for the image, then the request is served from the database. During this time, a copy of the image will be stored in the images folder and the index file also gets updated, so that the next request will not go to the database.

6.What happens I manually delete just the image file in the cache folder or the image file in the cache folder gets corrupted?

We will not see the image on the client page; we get a broken image ‘X’.

7.How are these cache files stored?

Filename.extension.cache is the file naming format.

8.What can I do if the cached file gets corrupted?

Recommendation: We can reset the index file. Site settings -> Site collection object cache -> Check the box for “Force this server to reset its disk based cache”. It will completely delete all the images and reset the bin files back to 1KB, so that next request will go to database and the complete index will get rebuilt.

Workaround: If you do not want to reset the complete index. Find out the missing image and copy just that file to the cache folder, name it as “filename.extension.cache”
Refresh the page now; it should pick up the image.

9.How is the Index file maintained?

Every time when the web.config initializes, the index file is loaded from the blobcache folder to memory. All new entries will keep getting updated in index file when in memory.
IISRESET /stop will flush the updated index file from memory to disc within the blobcache folder.
IISRESET /start will load the index file from blobcache folder to memory.
As long as the application pool is alive the index file will be getting updated in memory itself.

10.Can an Index file get corrupt?

Index file corruption is possible only when IIS crash or the index file is overwritten with wrong information. When IIS tries to load the index file from blobcache to memory and identifies that it is a corrupted file (not a valid file), it will get completely rebuilt (flush) as fresh file (1KB), all the old entries and images will be lost.

11.In a farm environment, is there any way of having all the WFEs' blob caches synchronized among each other?

No, this cannot be done because SharePoint maintains the index and the cache files individually on each server.

12.In a single WFE environment using web gardening, how does blob caching function? Is there any sync that happens among the working processes?

Web gardening is not supported.