Abstract: A graphical user interface based method of configuring automatic failover from a primary database system to a standby database system that is coupled to the primary database system by a network. Also coupled to the network is an observer process that is independent of the database systems and that initiates the failover process. The observer periodically pings the database systems to determine whether a failover is necessary. The graphical user interface permits a user to specify the primary and secondary database systems, configure the observer, and specify conditions under which a failover may occur and to enable automatic failover. A failover context is created from the inputs to the GUI and stored in persistent storage belonging to the database systems. If the Observer's context is stale, the Observer fetches the database system's context.

Abstract: A new virtual memory system is disclosed having a virtual address space including a gap of inaccessible virtual addresses within the virtual address space. A new virtual memory allocation routine is disclosed providing a starting address of accessible virtual addresses allocated to a currently executing process in a response to a request. The accessible virtual addresses are virtually contiguous, and include no addresses from within the gap of inaccessible virtual addresses. A new virtual memory deallocation routine is further disclosed providing deallocation of ranges of virtual addresses which may or may not include addresses within the inaccessible gap.

Abstract: A virtual memory system includes a virtual address space including a process private space, a shared space, and a page table space located between the process private space and the shared space. The page table space includes page table entries mapping both the process private space and the shared space to physical memory. The page table entries might include a set of virtually contiguous process private page table entries adjacent to the process private space, and a set of virtually contiguous shared page table entries adjacent to the shared space. The process private space may include virtual addresses on a first side of a private/shared virtual address boundary, and the shared space includes virtual addresses on a second side of the private/shared virtual address boundary.

Abstract: A new virtual memory system is disclosed having a virtual address space including a gap of inaccessible virtual addresses within the virtual address space. A new virtual memory allocation routine is disclosed providing a starting address of accessible virtual addresses allocated to a currently executing process in a response to a request. The accessible virtual addresses are virtually contiguous, and include no addresses from within the gap of inaccessible virtual addresses. A new virtual memory deallocation routine is further disclosed providing deallocation of ranges of virtual addresses which may or may not include addresses within the inaccessible gap.

Abstract: A new system and method for outswapping a process is disclosed. The new system forms one or more working set list chains (also referred to as "page table chains") during the outswap process. The new system then conveniently locates and outswaps a number of page table pages of the process to be outswapped by traversing the working set list chains. In a preferred embodiment, the forming of each working set list chain is performed while traversing a working set list during outswapping of a number of body pages of a process. Each working set list entry potentially describes a page of virtual memory in use by the process to be outswapped. In a further aspect of the disclosed system, traversing the working set list of the process to be outswapped includes determining whether each one of the working set list entries indicates a private page table page. If an entry in the working set list indicates a private page table page, the present system adds a link to a working set list chain.

Abstract: A system for accessing page table entries is disclosed. The system provides access to a page table entry mapping a predetermined physical page of memory. The system includes a physical page data base having an entry for each physical page of memory. Each physical page data base entry contains backlink information regarding an associated physical page of memory. The present system obtains a physical page data base entry associated with the predetermined physical page of memory from the physical page data base. The system uses a reserved page table entry, for example mapped by shared space, to build a virtual window. The virtual window provides a virtual address that may be used to access the page table entry mapping the predetermined physical page of memory. The virtual address provided by the virtual window is mapped to physical memory by the reserved page table entry.

Abstract: A virtual memory system is disclosed, providing a virtual address space of virtual addresses simultaneously available to a given process. The virtual address space includes a process private space accessible only to a given process, as well as a shared space of virtual addresses potentially accessible to two or more processes. The process private space includes virtual addresses on one side of a private/shared virtual address boundary, while the virtual addresses within the shared space are on the other side of the private/shared virtual address boundary. The private/shared boundary is ensured to be greater than a predetermined highest process private (or shared) virtual address of a different virtual memory system, and less than or equal to a predetermined lowest shared (or process private) virtual address of that different virtual memory system. Compatibility is ensured for software written for the different virtual memory system, allowing such software to run without modification on the present system.

Abstract: In accordance with principles of the invention there is disclosed a new system for accessing a page table structure of a non-current process. The new system modifies a current page table structure such that a process private portion of a current page table structure is replaced with a process private portion of the page table structure of the non-current process. After the necessary accesses have been performed, the present system again modifies the page table structure so that the process private portion of the current page table structure is restored to the process private portion of the page table structure of the current process. The new system does not require a complete context switch, and the target PTEs are advantageously mapped to the virtual memory locations in which they would normally reside if the target process was current.