Insomnia can be caused by psychiatric conditions such as depression. Psychological struggles can make it hard to sleep, insomnia itself can bring on changes in mood, and shifts in hormones and physiology can lead to both psychiatric issues and insomnia at the same time.
Lock modes specify different kinds of locks. The choice of which lock mode to apply depends on the resource that needs to be locked. The following three lock types are used for row-and page-level locking: 1  Shared (S). 2  Exclusive (X).3  Update (U).nce an exclusive lock is set for the page (or row), no other lock can be placed on the same resource. NOTE. The database system automatically chooses the appropriate lock mode according to the operation type (read or write). An update lock can be placed only if no other update or exclusive lock exists.
A database link (DBlink) is a definition of how to establish a connection from one Oracle database to another. The following link types are supported: 1  Private database link-belongs to a specific schema of a database.2  Only the owner of a private database link can use it.3  Public database link-all users in the database can use it. 4  Global database link-defined in an OID or Oracle Names Server.he following link types are supported: 1  Private database link-belongs to a specific schema of a database. 2  Only the owner of a private database link can use it. 3  Public database link-all users in the database can use it. 4  Global database link-defined in an OID or Oracle Names Server.