Explanation
The reason is that the build agent account doesn't have permission on your source tree to checkin other user's changes

Solution
You need to right click on the source tee in Source Control Explorer. Then click Properties and go to Security tab. You can then select the corresponding user of group and check the Allow checkbox for Check in other user’s changes.

Explanation:

The default value of work item attachments is 4KB.  Attachment size can be adjusted up to 2GB.

Solution:

Log in as TFS Admin on the TFS Application tier and use the following web services to increase the attachment size.

http://localhost:8080/tfs/<Collection Name>/WorkItemTracking/v1.0/ConfigurationSettingsService.asmx

Explanation

I have been in situation where the cache clean job doesn’t get enough time to clean up old cache data and the flow of TFS server cache is more than the cache clean up which leads to production server outage and performance issues. The workaround mentioned in this post is expensive! means, It will consume more server resource which will affect the TFS server performance.

The Cache Cleanup can take long time on a very large drive. I would recommand to go with the Recommanded Workaround without affecting the server performance rather than workaround.

Workaround

1. To redirect the cache to different drive

• Create a new cache folder in the drive with more free space.
• Open Properties dialog for the new cache folder
• On the Security tab, choose Edit --> The Permissions dialog box opens.
• Choose Add --> The Select Users, Computers, or Groups dialog box opens.
• Add the local group TFS_APPTIER_SERVICE_WPG, and then choose OK.
• Select the Modify check box, clear all other check boxes, and then choose OK.
• Open <TFS Server InstallDIR>\Application Tier\Web Services\web.config file
• Add a line to the appSettings section

              <add key="dataDirectory" value="new cache folder" />

• Save and close the web.config file.
• Wait for sometime (may be 2 mins) for new setting in web.config to take effect
• Delete the old cache root folder

2. To change Cache Settings limits

• Open <TFS Server InstallDIR>\Application Tier\Web Services\web.config file

          To specify a percentage of available disk space to fill before old files are removed, add the PercentageBasedPolicy element.

              <add key="PercentageBasedPolicy" value="60" />

          To specify a fixed size in MB for the cache to reach before old files are removed, add the FixedSizeBasedPolicy element.

              <add key="FixedSizeBasedPolicy" value="500" />

          To change the amount of cache to free when removing old files, add the CacheDeletionPercent element.

              <add key="CacheDeletionPercent" value="50" />

• Save and close the web.config file.
• Wait for sometime (may be 2 mins) for new setting in web.config to take effect

Example

<appSettings>
        <add key="applicationDatabase" value="Data Source=dbserverhere;Initial Catalog=Tfs_Configuration;Integrated Security=True;" />
        <add key="WorkItemTrackingCacheRoot" value="C:\Windows\Temp\TFTemp" />
        <add key="traceWriter" value="false" />
        <add key="traceDirectoryName" value="%TEMP%\\TFLogFiles" />
        <add key="applicationId" value="GUID here" />
        <!-- The new cache folder location. -->
        <add key="dataDirectory" value="new cache folder" />
        <!-- The cache should fill up to 60% capacity of available disk space before old files are removed.-->
 <add key="PercentageBasedPolicy" value="60" />
        <!-- The cache should reach 500 MB before old files are removed. -->
 <add key="FixedSizeBasedPolicy" value="500" />
        <!-- To free 50% of the cache when removing old files -->
 <add key="CacheDeletionPercent" value="50" />
</appSettings>

Thinks to know

The default is CacheLimitPercent = 75%
If both CacheLimitPercent and FixedSizeBasedPolicy are set, FixedSizeBasedPolicy wins.
If CacheDeletionPercent is not set, it defaults to 20%
Default cache location:  \%programfiles%\Microsoft Team Foundation Server <Version>\Application Tier\Web Services\_tfs_data

Recommanded Workaround without affecting the server performance

1. To Rebuild the cache without changing Cache Settings limits

• Create a temp cache folder in the drive with more free space.
• Open Properties dialog for the new cache folder
• On the Security tab, choose Edit --> The Permissions dialog box opens.
• Choose Add --> The Select Users, Computers, or Groups dialog opens.
• Add the local group TFS_APPTIER_SERVICE_WPG, and then choose OK.
• Select the Modify check box, clear all other check boxes, and then choose OK.
• Open <TFS Server InstallDIR>\Application Tier\Web Services\web.config file
• Comment dataDirectory element if already exist

              <!-- <add key="dataDirectory" value="Current cache folder" /> -->

              Note: Default cache location:  <TFS Server InstallDIR>\Version Control Proxy\Web Services\VersionControlProxy\Data

• Add a line to the appSettings section

              <add key="dataDirectory" value="temp cache folder" />

• Save and close the web.config file.
• Wait for sometime (may be 2 mins) for new setting in web.config to take effect
• Delete the content in current cache folder (Note: Do not delete the current cache folder, Only the folders and files inside current cache folder should be deleted)
• Open <TFS Server InstallDIR>\Application Tier\Web Services\web.config file
• Comment (temp) dataDirectory element

             <!-- <add key="dataDirectory" value="temp cache folder" /> -->

• UnComment dataDirectory element if already exist

             <add key="dataDirectory" value="Current cache folder" />

             Note: Default cache location: <TFS Server InstallDIR>\Version Control Proxy\Web Services\VersionControlProxy\Data

• Save and close the web.config file.
• Wait for sometime (may be 2 mins) for new setting in web.config to take effect