SQLOS is the base module in the SQL Server architecture. It implements functions normally linked with the Operating System: thread preparation, memory management, I/O management, buffer pool management, resource management, synchronization primitives and locking, and deadlock discovery. Because the requirements of SQL Server are highly dedicated, it equipment its own memory and thread management system, rather than using the generic one implement in the operating system. It divides all the operations it performs into a series of Tasks - both background preservation jobs as well as processing requests from clients. Internally, a pool of employee threads is maintained, onto which the tasks are listed. A task is associated with the thread until it is finished; only after its completion is the thread freed and returns to the pool. If there are no free threads to allocate the task to, the task is temporarily blocked. Each worker thread is map onto either an Operating System thread or a fiber. Fibers are user mode threads that implement co-operative multitasking. Using fibers means SQLOS does all the secretarial of thread organization itself, but then it can optimize them for its particular use. SQLOS also includes synchronization primitives for locking as well as monitoring for the employee threads to detect and recover from deadlocks.
Sunday, September 21, 2008
Microsoft SQL Server is a relational database management system (RDBMS) shaped by Microsoft. Its main query language is Transact-SQL, an completion of the ANSI/ISO standard Structured Query Language (SQL) new by both Microsoft and Sybase.
The design of Microsoft SQL Server is broadly divided into three mechanism: SQLOS which implements the basic services necessary by SQL Server, counting thread scheduling, memory administration and I/O management; the Relational Engine, which implements the relational database mechanism including support for databases, tables, queries and stored events as well as implement the type system; and the Protocol Layer which expose the SQL Server functionality.
Monday, September 08, 2008
A laptop computer or notebook computer is a little mobile computer, typically weighing 3 to 12 pounds, although older laptops may weigh up more. Laptops typically run on a single main battery or from an external AC/DC adapter that charge the battery while it also supplies power to the computer itself, even in the event of a power failure. This very potent main battery should not be confused with the much smaller battery nearly all computer use to run the real-time clock and backup BIOS configuration into the CMOS memory when the computer is lacking power.
Laptops contain mechanism that are similar to their desktop counterpart and perform the same functions, but are miniaturized and optimized for mobile use and efficient power expenditure, although typically less controlling for the same price. Laptops usually have liquid crystal display and most of them use different memory module for their random access memory, for instance, SO-DIMM in lieu of the larger DIMMs. In calculation to a built-in keyboard, they may utilize a touchpad or a point stick for input, though an outside keyboard or mouse can usually be attached.