Using view layer in database system for zero downtime upgrade

1. A computer-implemented method for minimizing downtime during execution of a maintenance procedure of a database system, the method being executed by one or more processors and comprising:

providing direct access by an application to a data persistency without passing through any view layer between sessions of the application and the data persistency within a database system;

adding a view layer in the database system as an intermediate layer between the application and the data persistency within the database system;

providing a first access schema in the view layer of the database system, the first access schema comprising one or more first database objects and one or more projection views, each projection view corresponding to a second database object of one or more second database objects in a data persistency of the database system;

transitioning access of sessions of the application from the data persistency of the database system from direct access to access through the first access schema;

executing at least a portion of the maintenance procedure in the database system, the at least a portion of the maintenance procedure:

changing one or more second database objects within the data persistency,

creating a second access schema, and

transitioning access of the sessions of the application from the first access schema to the second access schema;

transitioning access of the sessions of the application from access through the second access schema to the data persistency of the database system; and

removing the second access schema and the view layer from the database system to provide direct access by the application to the data persistency without passing through any view layer between sessions of the application and the data persistency within the database system.

2. The method of claim 1 , wherein each second database object in the one or more second database objects comprises content that one or more operations can be executed on.

3. The method of claim 1 , wherein each first database object in the one or more first database objects is absent content that one or more operations can be executed on.

4. The method of claim 1 , wherein transitioning access of sessions of an application from the data persistency of the database system to the first access schema comprises:

configuring a second database connection of a database interface of the application to connect sessions of the application to the first access schema; and

rolling sessions from a first database connection of the database interface to the second database connection.

5. The method of claim 1 , wherein transitioning access of the sessions of the application from the second access schema to the data persistency of the database system comprises:

configuring a second database connection of a database interface of the application to connect sessions of the application to the data persistency; and

rolling sessions from a first database connection of the database interface to the second database connection.

6. The method of claim 1 , wherein the one or more first database objects comprise one or more of a view, a filter rule, a dependency rule, and a stored procedure.

7. The method of claim 1 , wherein providing a first access schema in a view layer of the database system comprises:

for each second database object comprising a table, creating a projection view to the table as a first database object of the one or more first database objects; and

for each second database object comprising a sequence, creating a synonym to the sequence as a first database object of the one or more first database objects.

8. A non-transitory computer-readable storage medium coupled to one or more processors and having instructions stored thereon which, when executed by the one or more processors, cause the one or more processors to perform operations for minimizing downtime during execution of a maintenance procedure of a database system, the operations comprising:

providing direct access by an application to a data persistency without passing through any view layer between sessions of the application and the data persistency within a database system;

adding a view layer in the database system as an intermediate layer between the application and the data persistency within the database system;

providing a first access schema in the view layer of the database system, the first access schema comprising one or more first database objects and one or more projection views, each projection view corresponding to a second database object of one or more second database objects in a data persistency of the database system;

transitioning access of sessions of the application from the data persistency of the database system from direct access to access through the first access schema;

executing at least a portion of the maintenance procedure in the database system, the at least a portion of the maintenance procedure:

changing one or more second database objects within the data persistency,

creating a second access schema, and

transitioning access of the sessions of the application from the first access schema to the second access schema;

transitioning access of the sessions of the application from access through the second access schema to the data persistency of the database system; and

removing the second access schema and the view layer from the database system to provide direct access by the application to the data persistency without passing through any view layer between sessions of the application and the data persistency within the database system.

9. The non-transitory computer-readable storage medium of claim 8 , wherein each second database object in the one or more second database objects comprises content that one or more operations can be executed on.

10. The non-transitory computer-readable storage medium of claim 8 , wherein each first database object in the one or more first database objects is absent content that one or more operations can be executed on.

11. The non-transitory computer-readable storage medium of claim 8 , wherein transitioning access of sessions of an application from the data persistency of the database system to the first access schema comprises:

configuring a second database connection of a database interface of the application to connect sessions of the application to the first access schema; and

rolling sessions from a first database connection of the database interface to the second database connection.

12. The non-transitory computer-readable storage medium of claim 8 , wherein transitioning access of the sessions of the application from the second access schema to the data persistency of the database system comprises:

configuring a second database connection of a database interface of the application to connect sessions of the application to the data persistency; and

rolling sessions from a first database connection of the database interface to the second database connection.

13. The non-transitory computer-readable storage medium of claim 8 , wherein the one or more first database objects comprise one or more of a view, a filter rule, a dependency rule, and a stored procedure.

14. The non-transitory computer-readable storage medium of claim 8 , wherein providing a first access schema in a view layer of the database system comprises:

for each second database object comprising a table, creating a projection view to the table as a first database object of the one or more first database objects; and

for each second database object comprising a sequence, creating a synonym to the sequence as a first database object of the one or more first database objects.

15. A system, comprising:

a computing device; and

a computer-readable storage device coupled to the computing device and having instructions stored thereon which, when executed by the computing device, cause the computing device to perform operations for natural language explanations for minimizing downtime during execution of a maintenance procedure of a database system, the operations comprising:

providing direct access by an application to a data persistency without passing through any view layer between sessions of the application and the data persistency within a database system;

adding a view layer in the database system as an intermediate layer between the application and the data persistency within the database system;

providing a first access schema in the view layer of the database system, the first access schema comprising one or more first database objects and one or more projection views, each projection view corresponding to a second database object of one or more second database objects in a data persistency of the database system;

transitioning access of sessions of the application from the data persistency of the database system from direct access to access through the first access schema;

executing at least a portion of the maintenance procedure in the database system, the at least a portion of the maintenance procedure:

changing one or more second database objects within the data persistency,

creating a second access schema, and

transitioning access of the sessions of the application from the first access schema to the second access schema;

transitioning access of the sessions of the application from access through the second access schema to the data persistency of the database system; and

removing the second access schema and the view layer from the database system to provide direct access by the application to the data persistency without passing through any view layer between sessions of the application and the data persistency within the database system.

16. The system of claim 15 , wherein each second database object in the one or more second database objects comprises content that one or more operations can be executed on.

17. The system of claim 15 , wherein each first database object in the one or more first database objects is absent content that one or more operations can be executed on.

18. The system of claim 15 , wherein transitioning access of sessions of an application from the data persistency of the database system to the first access schema comprises:

configuring a second database connection of a database interface of the application to connect sessions of the application to the first access schema; and

rolling sessions from a first database connection of the database interface to the second database connection.

19. The system of claim 15 , wherein transitioning access of the sessions of the application from the second access schema to the data persistency of the database system comprises:

configuring a second database connection of a database interface of the application to connect sessions of the application to the data persistency; and

rolling sessions from a first database connection of the database interface to the second database connection.

20. The system of claim 15 , wherein the one or more first database objects comprise one or more of a view, a filter rule, a dependency rule, and a stored procedure.