2 operating system in 1989 – and extends sql server 2005 express edition download 32 bit the current day. 2 in 1989, by Sybase, Ashton-Tate, and Microsoft. 2 for NT is released in 1993, marking the entry onto Windows NT.
Intended for use as an application component, it did not include GUI management tools. Later, Microsoft also made available a web admin tool. Initially designed and developed by Sybase Inc. Data storage is a database, which is a collection of tables with typed columns. Storage space allocated to a database is divided into sequentially numbered pages, each 8 KB in size. A page is marked with a 96-byte header which stores metadata about the page including the page number, page type, free space on the page and the ID of the object that owns it. A table is split into multiple partitions in order to spread a database over a computer cluster.
Any 8 KB page can be buffered in-memory, and the set of all pages currently buffered is called the buffer cache. The buffer cache is managed by the Buffer Manager. Either reading from or writing to any page copies it to the buffer cache. As such, it needs to control concurrent access to shared data, to ensure data integrity—when multiple clients update the same data, or clients attempt to read data that is in the process of being changed by another client. Locks can be applied on different levels of granularity—on entire tables, pages, or even on a per-row basis on tables. For indexes, it can either be on the entire index or on index leaves.
The level of granularity to be used is defined on a per-database basis by the database administrator. While a fine-grained locking system allows more users to use the table or index simultaneously, it requires more resources, so it does not automatically yield higher performance. The mechanism allows a new version of a row to be created whenever the row is updated, as opposed to overwriting the row, i. ID of the transaction that created the version of the row.