Site Collection Locks in SharePoint

Locks can be Set/Reset in 4 ways:

1. Using Web User Interface - Through Central Administration
2. Using STSADM 
3. Using PowerShell
4. Using Object Model
1. By .Net code
2. By PowerShell

Using Web User Interface: 
Where to Look? Go to Central Administration > Application Management > Configure Quotas and Locks >Select Site collection >Select lock status option

STSADM:

To set Lock:
stsadm -o setsitelock -url <Site-collection-url> -lock <Lock-Type>

To Check current locks applied:
stsadm -o getsitelock -url <Site-collection-url>

Where <Lock-Type> can take one of the following value: 

• none  - Removes all the locks
• noadditions  - Prevents from Addition
• readonly - Can't add/Update/Delete content
• noaccess - You can't view the site at all

PowerShell:
Set-SPSite -Identity <Site-collection-url> -LockState <Lock-State>

Where: <Lock-State> can be:

•     ReadOnly
•     Unlock
•     NoAdditions
•     NoAccess 

Ex. 

$site = Get-SPSite -Identity <site url>
$site.readonly = $false 

Object Model:
You can Programmatically set the Lock status using SPSite object's Properties:

•     SPSite.ReadLocked
•     SPSite.WriteLocked
•     SPSite.ReadOnly

Code Sample :

    using (SPSite site = new SPSite("http://spserver2:3030"))

                {

                    using (SPWeb sharePointWeb = site.RootWeb)

                    {

                        site.AllowUnsafeUpdates = true;

                        sharePointWeb.AllowUnsafeUpdates = true;

                     

                        site.ReadOnly = true;

                        site.LockIssue = "Tesing Lock";

                        site.AllowUnsafeUpdates = false;

                        sharePointWeb.AllowUnsafeUpdates = false;

                     }

                 }