The logs are text files named in the following format

The logs are text files named in the following format:
 Upgrade-YYYYMMDD-HHMMSS-SSS-error .log
 Upgrade-YYYYMMDD-HHMMSS-SSS .log
Where
 YYYYMMDD is the date
 HHMMSS-SSS is the time (hours in 24-hour clock format, minutes, seconds, and milliseconds)
An example for an upgrade error log is Upgrade-20120105-132126-374-error.log, and an
example for an upgrade log is Upgrade-20120105-132126-374.log.
Note:
The format of the upgrade log for SharePoint 2013 is based on the same structure as
ULS.
The upgrade log file includes the name of the content database being upgraded.
To view upgrade status for all databases by using Windows PowerShell
1. Verify that you have the following memberships:
 securityadmin fixed server role on the SQL Server instance.
 db_owner fixed database role on all databases that are to be updated.
 Administrators group on the server on which you are running the Windows PowerShell cmdlets.
An administrator can use the Add-SPShellAdmin cmdlet to grant permissions to use
SharePoint 2013 cmdlets.

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Note:
If you do not have permissions, contact your Setup administrator or SQL Server
administrator to request permissions. For additional information about Windows
PowerShell permissions, see Add-SPShellAdmin .
2. Start the SharePoint 2013 Management Shell.
 For Windows Server 2008 R2:
 On the Start menu, click All Programs , click Microsoft SharePoint 2013 Products , and
then click SharePoint 2013 Management Shell .
 For Windows Server 2012:
 On the Start screen, click SharePoint 2013 Management Shell .
If SharePoint 2013 Management Shell is not on the Start screen:
 Right-click Computer , click All apps , and then click SharePoint 2013 Management Shell .
For more information about how to interact with Windows Server 2012, see Common
Management Tasks and Navigation in Windows Server 2012 .
3. At the Windows PowerShell command prompt, type the following command:
Windows PowerShell
Get-SPContentDatabase | ft Name, NeedsUpgradeIncludeChildren
This cmdlet returns a table-style list of databases in your farm and indicates whether the database
needs an upgrade to SharePoint 2013.
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Attach the remaining databases
After you restore the first content database and verify success, you can continue to restore and
upgrade other databases. You can perform parallel database attach upgrades to upgrade more than
one database at a time. Use separate Command Prompt windows to run multiple upgrades. It is
recommended that you separate the start time for each new database upgrade session by several
minutes to prevent issues with temporary locks set for the web application during attachment.
Otherwise you might receive an error on the upgrade session. The wait time to clear temporary locks
varies depending on the number of site collections, or the speed of the database server hardware.