User Provisioning? User Provisioning Requests?

User Provisioning:
User Provisioning meaning what we can do on User object in salesforce.

We can do following operations on user woth the user provisioning requests,

EVENT	OPERATION	OBJECT
Create user	Create	User
Update user (for selected attributes)	Update	User
Disable user	Deactivate	User
Enable user	Activate	User
Freeze user	Freeze	UserLogin
Unfreeze user	Unfreeze	UserLogin
Reactivate user	Reactivate	User
Change user profile	Create or Deactivate	User
Assign or unassign a permission set to a user	Create or Deactivate	PermissionSetAssignment
Assign or unassign a profile to the connected app	Create or Deactivate	SetupEntityAccess
Assign or unassign a permission set to the connected app	Create or Deactivate	SetupEntityAccess

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Granular Locking [ https://developer.salesforce.com/docs/atlas.en-us.draes.meta/draes/draes_tools_granular_locking.htm ]

By default, the Lightning Platform locks the entire group membership table to protect data integrity when Salesforce makes changes to roles and groups. This locking makes it impossible to process group changes in multiple threads to increase throughput on updates. 

When the granular locking feature is enabled, the system employs additional logic to allow multiple updates to proceed simultaneously if there is no hierarchical or other relationship between the roles or groups involved in the updates. Administrators can adjust their maintenance processes and integration code to take advantage of this limited concurrency to process large-scale updates faster, all while still avoiding locking errors.

The key advantages of granular locking are that:

• Groups that are in separate hierarchies are now able to be manipulated concurrently.
• Public groups and roles that do not include territories are no longer blocked by territory operations.
• Users can be added concurrently to territories and public groups.
• User provisioning can now occur in parallel.
  • Portal user creation requires locks only if new portal roles are being created.
  • Provisioning new portal users in existing accounts occurs concurrently.
• A single-long running process, such as a role delete, blocks only a small subset of operations.

https://help.salesforce.com/articleView?id=000325942&language=en_US&type=1&mode=1

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