sObjects That Don’t Support DML Operations

Your organization contains standard objects provided by Salesforce and custom objects that you created. These objects can be accessed in Apex as instances of the sObject data type. You can query these objects and perform DML operations on them. However, some standard objects don’t support DML operations although you can still obtain them in queries. The following is a non-exhaustive list of such objects:

AccountTerritoryAssignmentRule
AccountTerritoryAssignmentRuleItem
ApexComponent
ApexPage
BusinessHours
BusinessProcess
CategoryNode
CurrencyType
DatedConversionRate
NetworkMember (allows update only)
ProcessInstance
Profile
RecordType
SelfServiceUser
StaticResource
Territory2
UserAccountTeamMember
UserPreference
UserTerritory
WebLink

The following are special cases of DML operations on objects.

If an Account record has a record type of Person Account, the Name field can’t be modified with DML operations.
All standard and custom objects can also be accessed through the SOAP API. ProcessInstance is an exception. You can’t create, update, or delete ProcessInstance in the SOAP API.
DML operations aren't supported on Data Cloud data model objects (DMOs). For details on using Apex with Data Cloud objects, see Data Cloud in Apex.

To determine if DML is supported on your specific object, use the Schema.describeSObjects()method as shown in this sample code.

1// This example describes the ApexPage object. Replace it with your
2// objects(s) in the results list to check if DML is permitted.
3List<Schema.DescribeSobjectResult> results = Schema.describeSObjects(new List<string>    {'ApexPage'}, SObjectDescribeOptions.DEFERRED);
4DescribeSObjectResult d = results[0];
5System.debug('isCreateable():' + d.isCreateable());
6System.debug('isUpdateable():' + d.isUpdateable());
7System.debug('isQueryable(): ' + d.isQueryable());

Apex Developer Guide

sObjects That Don’t Support DML Operations