system.security.securityexception: request for the permission of type 'system.security.permissions.securitypermission, mscorlib, version=2.0.0.0, culture=neutral, publickeytoken=b77a5c561934e089' failed

Reference:
http://codesnipets.wordpress.com/2010/12/25/sharepoint-2010-and-asp-net-web-application-security-exception/

You might get following error “System.Security.SecurityException: Request for the permission of type ‘System.Security.Permissions.EnvironmentPermission, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089′ failed.“

specially when you have asp.net web application configured under Share point Virtual Directoryand you try to access web service or write a log file or try to call method from custom assembly.

The reason you get this error is your asp.net web application runs under WSS_Minimal trust.

Solution

In IIS, Select your sharepoint virtual directory and go to Features view.

In features view select .NET Trust Levels.

In .NET Trust Level you will see default WSS_Minimal trust. Change it to Full Trust and re-start web application.

Add/ Edit Permission Level Sharepoint

SharePoint Groups or accounts such as a domain user or domain group can be assigned permissions to a SharePoint object such as a Site, List, Library, Folder or List Item. Permission Levels such as Contribute and Read are made up of individual permissions. Within this section we will explore the Out-of-the-Box permissions levels before exploring how we can create custom permission levels.

Out-of-the-Box Permission Levels

To access the Out-of-the-Box permissions, choose Site Actions, Site Permissions. You will be able to see a list of users/groups that have permission to your team site. Within the Permission Tools ribbon, click Permission Levels to see the existing permission levels.

Figure 11 – Accessing Permission Levels

The Out-of-the-Box permission levels include:

Full Control	User will receive every SharePoint Permission unless the permission has been removed via a Permission Policy. The permission level cannot be modified.
Design	Users with Design Permissions can virtually do everything with the exception of Manage Permissions on the Site, View Web Analytics Data, Create Subsites, Manage Web Site, Create Groups, Enumerate Permissions and Manage Alerts. Users with this permission level can create, edit and delete list items as well as make design changes to the Shared views of the site and lists.
Contribute	Contributers can create, edit, and delete items within lists and libraries. They have the same restrictions as Design plus they cannot manage the look and feel of sites or shared views. They cannot apply themes, styles, or modify pages.
Read	Readers have the same restrictions as Contributers. In addition they cannot Create, Edit or Delete Items. They can only open items to read them. They also do not get any personal permissions and therefore cannot add or remove personal web parts, manage personal views or edit personal user information.
Limited Access	Limited Access provides you enough permissions to navigate to an item that you do have permission to. For example, you may have been granted Read permissions to a Document within a library that had broken permission inheritance. If you did not have permissions granted to you for the site or library that contained the document, you would be granted limited access which allows you to navigate to the document without seeing any other content. Limited Access is often incorrectly reported in the permission reports. E.g. A user may have Full Control to a Site via a Domain Group. They are also granted permissions directly to a document. The user would then be listed as having Limited Access instead of Full Control to the Team Site.
View Only	The same as read but cannot download documents. Can only view them in the browser.
Approve	Very similar to contribute but also has Approve Items permission.
Manage Hierarchy	Virtually the same as Full Control but does not have Design change options such as apply theme. Used by users who are likely to move sites around.
Restricted Read	Can view pages and documents, but cannot view historical versions or user permissions.

Creating Custom Permission Levels

You can change the existing permission levels or create your own permission levels at the root site level in the site collection only. In SharePoint 2007, this could be done at sub site level. It is possible to break permission level inheritance but only through the Object Model but that is beyond the scope of this article. You will find a good explanation here: http://stackoverflow.com/questions/7038444/programatically-break-permission-level-inheritance

Note: I would recommend never changing the existing permission levels as that would be very confusing to users who expect a permission level to behave within a certain way.

The reason for creating a custom permission level will be specific to your needs. It might be that you want for example a permission level that lies somewhere between Read and Contribute. Perhaps you want users to be able to Add and Edit items but not Delete.

You can create a custom permission level in two ways. Firstly, you can create them from scratch and select each permission that you would like the permission level to have. Or you can copy an existing permission level, provide it a new name, and then apply the changes to the new copy.

To create a new permission level from scratch:

1. 1. Ensure that you are a Site Owner with the Manage Permissions role.
2. 2. Click Site Actions, Site Permissions.
3. 3. Click the Permission Levels button
4. 4. Click the Add a Permission Level action button.
5. 5. Provide a Name and Description for your custom permission level.
6. 6. Check the Site, List, and Personal permissions that you wish to grant to the permission level.
7. 7. Click Create.

Figure 12 – Creating a custom permission level from scratch.

To create a custom permission level by copying an existing permission level:

1. 1. Ensure that you are a Site Owner with the Manage Permissions role.
2. 2. Click Site Actions, Site Permissions.
3. 3. Click the Permission Levels button
4. 4. Click on an existing permission level such as Contribute.
5. 5. Scroll to the bottom of the page.
6. 6. Click the Copy Permission Level button.

Figure 13 – Copying a Permission Level.

7. Provide a Name and Description for your custom permission level.

8. Make the desired changes by selecting or deselecting the permissions check boxes.

Assigning Permissions Levels

Permission Levels can be assigned to Users, Local Groups or Domain Groups as well as SharePoint Groups. There are different opinions on what you should do. However, my personal preference is to use add domain groups to SharePoint Groups in order for permissions to be granted rather than assigning domain groups permissions directly. Within your environment, you may find granting permissions directly to Active Directory users or groups works best.

To assign permissions to a SharePoint Group:

1. 1. Choose Site Actions, Site Permissions.
2. 2. Check the box of the group that you would like to modify.
3. Click the Edit User Permissions button

Figure 14 – Editing permissions for a SharePoint group

3. Check the permission level that you would like to grant to this SharePoint Group.

Figure 15 – Assigning the custom permission level

Manage lists and libraries with many items

Overview of lists and libraries with many items

SharePoint 2010 supports very large lists and libraries. The following table summarizes the specifications and limits for lists and libraries that contain many items.

FEATURE	MAXIMUM LIMIT
Number of items in a list or library	50 million
Size of an individual file item or item attachment	2 Gigabytes

As you can see, you can store a lot of data and files in lists and libraries. But if a query or database operation exceeds a resource throttle or limit, you may be blocked from doing this operation because accessing that many items could adversely affect other users of the site. Fortunately, there are a set of straightforward strategies and basic features you can use to achieve the results you want to prevent you from exceeding these throttles and limits. All users can circumvent the limit during a dedicated time window, and with appropriate permission you can also use a higher limit through code.

Why is 5,000 such a magic number?

To minimize database contention, SQL Server often uses row-level locking as a strategy to ensure accurate updates without adversely impacting other users who are accessing other rows. However, if a read or write database operation, such as a query, causes more than 5,000 rows to be locked at once, then it's more efficient for SQL Server to temporarily escalate the lock to the entire table until the database operation is completed. Note that the actual number is not always 5,000, and can vary depending on your site, the amount of activity in the database, and your site's configuration. When this lock escalation occurs, it prevents other users from accessing the table. If this happens too often, then users will experience a degradation of system performance. Therefore, thresholds and limits are essential to help minimize the impact of resource-intensive database operations and balance the needs of all users.

What happens behind the scenes when you access many items in a list or library?

The following diagram summarizes the key points about what happens behind the scenes when you access many items in a list or library.

 Information workers can use appropriate views, styles, and page limits to speed up the display of data on the page.

 Filtered views with column indexes (and other operations) create database queries that identify a subset of columns and rows and return this subset to your computer.

 Farm administrators can specify dedicated time windows for all users to do unlimited operations during off-peak hours.

 Privileged developers can use object model overrides to temporarily increase thresholds and limits for custom applications.

 Thresholds and limits help throttle operations and balance resources for many simultaneous users.

 List or library data in a site collection is stored in a SQL Server database table, which uses queries, indexes and locks to maintain overall performance, sharing, and accuracy.

Resource throttles and limits

The following table summarizes information about resource throttles and limits that you need to be aware of. These throttles and limits are set on the Resource Throttling page in Central Administration. Contact your administrator for specific limits and requests for your site.

 NOTE   To assist central administration, the computer administrator of the front-end computer and the central administrator site owner accessing a list or library with many items are not subject to the following resource throttles and limits.

THRESHOLD  OR LIMIT	DEFAULT VALUE	DESCRIPTION
List View Threshold	5,000	Specifies the maximum number of list or library items that a database operation, such as a query, can process at one time. Operations that exceed this limit are blocked. To give you time to make alternative plans, SharePoint 2010 warns you on the List Settings page when your list has exceeded 3,000 items. The warning contains a help link to this topic.
Unique permissions limit	50,000	Specifies the maximum number of unique permissions allowed for a list or library. Every time you break the inheritance of permissions for an item or folder, it is counted as 1 unique permission toward this limit. If you try to add an item that would lead to exceeding this limit, you are prevented from doing so.
Row size limit	6	Specifies the maximum number of table rows internal to the database used for a list or library item. To accommodate wide lists with many columns, each item is wrapped over several internal table rows, up to 6 rows and up to a total of 8,000 bytes (excluding attachments). For example, if you have a list with many small columns, one that contains hundreds of Yes/No columns, then you could exceed this limit, in which case you would not be able to add more Yes/No columns to the list, but you still may be allowed to add columns of a different type.  NOTE   Farm administrators can only set this limit by using the object model, not through the user interface.
List View Lookup Threshold	8	Specifies the maximum number of join operations, such as those based on lookup, Person/Group, or workflow status columns. If the query uses more than eight columns, the operation is blocked. However, it is possible to programmatically select which columns to use by using maximal view, which can be set through the object model.
List View Threshold size for auditors and administrators	20,000	Specifies the maximum number of list or library items that a database operation, such as a query, can process at one time when performed by an auditor or administrator with appropriate permissions. This setting works in conjunction with Allow Object Model Override.
Allow Object Model Override	Y	Specifies whether or not developers can perform database operations, such as queries, that request an override of the List View Threshold to the higher limit specified by the List View Threshold for auditors and administrators. A farm administrator must enable an object model override, and then developers with appropriate permission may then programmatically request that their query use the higher List View Threshold to take advantage of it.
Daily time window	None	Specifies a time period during which resource thresholds and limits are ignored. A farm administrator can configure a time window during "off-peak" hours in 15 minute increments and up to 24 hours, such as, 6:00 PM to 10:00 PM or 1:30 AM to 5:15 AM.  NOTE   A database operation or query started within the daily time window continues until completion (or failure) even if it doesn't finish within the specified time window.

Ways to manage lists and libraries with many items

The following sections provide recommendations, techniques, and tips for ensuring that you and other users can quickly access many items in a list or library and help to keep your site operating smoothly.

Creating SharePoint indexed columns

To help improve the performance of a large list or library, you can index up to 20 columns. In general, an index on a column enables you to quickly find the rows you want based on the values in that column, even when working with millions of items. When you combine indexes with filtered views, you can quickly retrieve the items you want.

It is important to consider the following when you create and use indexed columns. Each additional column index consumes extra resources in the database and adds some overhead to every operation to maintain the index. Therefore, you should add indexes only to columns that will be used actively for filtering in views on the list or library. It's a good idea to look at all the views and see which columns are used most commonly across different views for filtering to help choose the right columns to be indexed. Note that any column that you define to have a unique value requires an index.

The following table summarizes what columns can and cannot be indexed.

SUPPORTED COLUMN TYPES	UNSUPPORTED COLUMN TYPES
Single line of text	Multiple lines of text
Choice (single value)	Choice (multi-valued)
Number	Calculated
Currency	Hyperlink or Picture
Date and Time	Custom Columns
Lookup (single value)  NOTE   Indexing the column in the other list or library does not improve performance of the lookup operation.	Lookup (multi-valued)
Person or Group (single value)	Person or Group (multi-valued)
Yes/No	External data
Managed Metadata

For steps on how to create an indexed column, see the section Create a simple or compound index in this topic.

Creating filtered views based on column indexes

For a view to quickly filter through a large number of items, the first column that you specify in the filter must be indexed. Other columns you specify in the view filter may or may not be indexed, but the view does not use those indexes. You also need to make sure that the first column of the filter does not return more items than the List View Threshold, even if the final result of the filtered view returns less than the List View Threshold. If the first column of the filter returns more items than the List View Threshold, you can use a filter with two or more columns When you define a filtered view that uses two or more columns, using an AND operator will usually limit the total number of items returned. But even in this case, you still need to specify as the first column in the filter the column that most likely returns the lesser amount of data. Note that using an OR filter almost always increases the number of items returned and won't be effective under these circumstances.

 IMPORTANT    If you are filtering a list by an indexed field, check your recycle bin for deleted items. Items in the recycle bin aren't actually deleted from the backend database until they are removed from the recycle bin. If the total number of filtered items in the list and in the recycle bin is greater than the List Threshold limit, then you may get an incomplete set of results, or none at all.

 NOTE   If you are a developer, you can programmatically use a compound index on the first column. A compound index is based on two columns, primary and secondary, and can use either column to access the data quickly.

The following are some suggestions for typical views that would work well with indexed columns:

TO FILTER BY:	INDEX THE:	FOR EXAMPLE:
Recently changed items	Modified column	To view only items that have changed in the past week, apply the filterModified is greater than  [Today]-7
New items	Created column	To create a view of only those items that were added in the past week, apply the filter Created is greater than [Today]-7
My items	Created Bycolumn	To create a view of only those items that you added, apply the filter Created By is equal to [Me]
Items due today	Due Datecolumn (created by you in a list or library)	To create a view of only those items with a due date of today, apply the filterDue Date is equal to [Today]
Discussion board updates	Last Updatedcolumn	To create a view of only the discussions that were updated in the past month, apply the filter Last Updated is greater than [Today]-30.
Archive files in a document library	Date Modified	To create a view of documents not changed since the year 2006 (that you then want to archive), apply the filter Date Modified is less than December 31st 2006
Find a subset of financial data	Region, Year (as two simple indexes)	To create a view of financial data for the NorthEast region in 2008, apply the filter Region equals "NE" AND Year equals 2008 because the Region column is likely to have less values than the Year column

Find links to more information about creating or changing views and about formulas and functions that you can use to filter views in the See Also section.

 NOTE   Even when you create a filtered view based on column indexes, certain additional operations might still be blocked because they require accessing the entire list or library. These operations include the following: adding or deleting an index, creating a sort in the view definition; displaying a column total; and adding, updating, or deleting calculated fields.

Organizing items into folders

Although folders (also called containers) are not required to use large lists and libraries, you can still use them to help organize your data and improve the efficiency of your data access. When you create a folder, behind the scenes you are creating an internal index. This internal index is also created for the root folder, or top-level of a list or library. When you access items in a folder, you are effectively using this internal index to access the data. Bear in mind that if a folder contains subfolders, each subfolder is counted as an item (but not any items in that subfolder).

Even when the total number of items in a list or library is very large, a view of a single folder is at least as fast as a view that filters the total number of items by using an indexed column. In some scenarios, it may be possible to distribute all of the items in a list or library into multiple folders such that no folder has more than five thousand items.

It is important to consider the following when you use folders to organize a large list or library:

·         A folder can contain more items than the List View Threshold, but to avoid being blocked by SharePoint 2010, you may still need to use a filtered view based on column indexes.

·         If you choose the Show all items without folders option in the Folders section when you create or modify a view in this list or library, you must then use a filter that is based on an index to ensure you don't reach theList View Threshold.

·         It is often useful to make the default view show all the available folders without any filtering so that users can choose the appropriate folder when they insert new items. Displaying all the folders also makes it less likely that items will be incorrectly added outside the folders in the list or library. Note that, unlike libraries, there is no automatic way to move items between folders in a list.

Controlling the display of data on the page

Once the subset of data has been transferred to your computer, there are additional strategies you can use to speed up the display of the data in your browser.

As you increase the size of the HTML source code behind a web page, there is usually a corresponding increase in time to render the page. The larger the page, the longer it takes to display. For example, the default style for a list or library view is the table style, which displays all the data, one item per table row, on one page. Therefore the more rows you display, the longer it takes to display the data.

Setting an item limit on a page

By setting an item limit on a page, you can directly control how many items display at one time by using a specific number, the default being 30.

There are two options you can choose when setting an item limit on a page:

·         If you select Display items in batches of the specified size (for paging), then you are creating a page-by-page display of the data which is useful when you are browsing items in a non-interactive way.

·         If you select Limit the total number of items returned to the specified amount, then you are creating a hard limit that may or may not return the entire results of your filter operation, but may be useful when testing your view, creating a prototype, or you only want to retrieve the top values in a view.

Using the Preview Pane view style

To see all of the information from items in your list in a vertical pane format, use the Preview Pane style. You can more quickly navigate the data by hovering over the item title in a scrolling region on the left side of the page, to see all the column values of the current item vertically listed on the right side of the page. Less initial data is displayed, and this helps display the view faster. This style is also very useful when your list is wide or has many columns and would require horizontal scrolling to see the data.

Using the Group By view style

The Group By view style groups the data by a category (up to two levels) that you choose when defining the view, which makes the initial display of the list view much smaller. You click a Plus/Minus button to expand/collapse a specific group of data and only load the subset of data that is needed onto the current page. This view style not only limits the display of the data, but also the retrieval of the data. Make sure that the default Show Grouping option is set to Collapsed. You can also control the paging of the grouped data in the same way as data that is not grouped. In some situations, such as simple reporting or drilling down and drilling up to find and update data, this view style can be much more efficient for users to use.

Using Datasheet view

Datasheet view is based on an ActiveX control and specifically designed to load data faster by retrieving and updating data asynchronously. This view makes it much more efficient to scroll, edit, and work with a lot of data, and is especially useful for doing frequent adds, updates, and comparisons to your data. Without disrupting your work, your changes are sent to the server, status is communicated to you by using icons, your changes are efficiently synchronized to the server and you can quickly resolve occasional conflicts. Datasheet view respects view filter, sort, and folder settings, but is not designed to work with page limits, dynamic filters and sorts in Standard view, or other non-tabular view styles, such as Group By and Preview Pane.

 TIP   If your list is organized by folders and you would like to see all the data in Datasheet view without the folders (a "flattened" view), you can set the view to see all items without folders. However, you may need to use a filter that is based on indexed columns to avoid reaching the List View Threshold.

Using the daily time window

The daily time window is a way for farm administrators to specify a dedicated time period for all users to do unlimited operations during off-peak hours, such as 6:00 PM to 10:00 PM.

Although views are a primary way to retrieve items from a list or library, other SharePoint commands and operations also require accessing the items in a list or library, such as: adding and deleting an index, adding and modifying a list column, deleting and copying folders, changing security settings for a list or library, saving a list with its content as a template, deleting a web or site, and restoring or deleting items from the Recycle Bin. These commands and operation could also fail if they exceed the site thresholds and limits when retrieving list data.

If you are not a developer or don't have convenient access to developer resources to do these operations for you, you can defer these types of operations to the daily time window. If the regular daily time window period is set up during normal sleeping hours, you can ask the farm administrator to move the time period to an early morning or late evening hour.