How to save SharePoint to be locked/ Unable to do any operation on SharePoint rather than read only

[Possible Cause]

This issue might be caused by backup failure
You may read here for details
http://technet.microsoft.com/en-us/library/ee748617.aspx

If the site collection’s Lock status is set to Not locked or Adding content prevented, Microsoft SharePoint Server 2010 temporarily sets the site to Read-Only while the backup operation is occurring. SharePoint Server 2010 does this to reduce the possibilities of users changing the site collection while it is being backed up. After the backup is finished, the setting is changed back its normal status.

[Solution]

To lock or unlock a site collection by using Central Administration

1.       Verify that you have the following administrative credentials.

• You must be a member of the Site Collection Administrators group for the site collection.

2.       In Central Administration, click Application Management.

3.       On the Application Management page, in the Site Collections section, click Configure quotas and locks. The Site Collection Quotas and Locks page opens.

4.       If you want to change the selected site collection, in the Site Collection section, on the Site Collection menu, click Change Site Collection. Use the Select Site Collection page to select a site collection.

5.       On the Site Collection Quotas and Locks page, in the Site Lock Information section, select one of the following options:

  Not locked: To unlock the site collection and make it available to users

While taking site collection backup(to prevent it to locked) –

1. Click SharePoint 2010 Management Shell.
2. At the Windows PowerShell command prompt type the following command:

Backup-SPSite -Identity <Site collection name> -Path <backup file> [-Force] [-NoSiteLock] [-UseSqlSnapshot] [-Verbose]