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The purpose of the ESE is to save and manage data through indexing and sequential access. Numerous Windows components such as Desktop Search, Active Directory use the ESE. It provides a collision recovery mechanism in order to maintain data consistency in times of system event occurrence. The ESE is suitable for server applications because it supports realtime transactions. The ESE cache guarantees high data access performance. Moreover, the ESE is light enough to be fit for auxiliary applications.

A database is an object which groups data physically, logically. la gastronomia The ESE database seems to be a single file in Windows, but internally it is a set of pages whose sizes are 2, 4, 8, 16, 32 KB and managed in a B-tree structure. (16 and 32 KB papges are used only in Windows 7, Exchange 2010, and higher versions). These pages include a database, data itself, an index for managing data orders, and meta data for describing data included in other information. A database can include up to 8 KB-sized pages, 16 TB data, and 232 pages.

A table is a homogeneous set of records. Each record has the same column set. Each table is identified by table names, and its range is bound by database. The size of disk space allotted to tables in a database is determined by parameters given when the tables are created through the CreateTable operation. Tables are increased automatically as data is written. Tables have at least one index. electric utility companies in arizona In a record data, there is at least one clustered index. If a cluster index is not defined in an application, an artificial index is created according to the time order of record insertion, to cluster and arrange records. Indexes are defined to sustain the data order, and enables data access by index order and column value. ESE’s clustered index is important that an index key should be unique. A clustered, or non-clustered index is indicated by using B-tree.

If insertion and update commands exceed a page, then the page is divided. A new page is allotted between the two pages which are previously adjacent in a logical sense. The ESE features on-line compression to re-compress data. If frequent updates are excepted in a table, a space for future data insertion is reserved by designating a proper page density when creating a table or an index, which helps to avoid or delay a split command.

The ESE database is composed of groups called instances. Most applications use a single instance. But all application can use several instances. Through these instances, more than one database can be connected with recovery log files. electricity questions and answers pdf Currently, up to 6 user databases can be attached to the ESE instance. Each process that ESE uses can have up to 1024 ESE instances.

A database can be separated from the ESE instances under execution, and later attached to the same or other instances under execution. During separation, the database is copied, using Standard Windows utility. It cannot be copied when opened independently and used in the activated state. The database can be operated in any devices that physically support Windows I/O commands for direct address designation.

A record is related to the set of column values. Records are inserted and updated through Update command, and deleted through Delete command. Columns are configured and retrieved through SetColumns and RetrieveColumns commands. The maximum size of a record 8,110 bytes, except for Long value columns, in case that the page size 8 KB. LongText and LongBinary column types have no size bound. Records can contain data bigger than the size of database when the data is saved in long value columns. gas jockey Only 9-byte internal data is required when long value reference is stored in records, and this long value can support up to 2 GB.

The column type of a long text and a long binary is a big-sized binary entity. This entity is saved in B-tree, and indexed by a column ID and a byte offset. The ESE supports append, byte-ranged-overwrite, and size designation. Also, ESE can save a single instance and thereby refer to multiple records for a binary entity. The maximum size of Long Text and Long Binary columns is 2 GB.

The ESE logging and recovery functions guarantee data integrity and consistency against system crash. Logging is a process that records update information of database. The structure of log files is very safe against system crash. If a system crashes, The log files are used to turn database into consistent state. gas monkey monster truck hellcat They can also protect data from media error. ESE supports on-line backup function to copy a database and log files without influencing database operations. Through this, a database can process query and update while backup is done.

There are multiple tables inside ESE database, and table information is managed by a catalog table called MSysObject. Certain tables include sub-tables called LV, in order to save big-sized data. Tables have their own identification numbers, known as Father data page (FDP). This is specified in all page headers in tables. The sub-tables called LV also use distinct FDP numbers, and are managed in the same way as the superordinate table .

In the database header, there is an unique signature in hexadecimal, and database state items and page size information are saved. The database header is important information that determines ESE database analysis methods, and combined with page numbers helps to find a page offset. The flowing figures show the database header format in hexadecimal.

A page is a logical unit used to save and mange records in the ESE database, and composed of header, data, and tag areas. The following figure demonstrates the structure of a page. In the header, there is an item, expressed as Available Page Tag in the figure, that represents the number of tags, and this value corresponds to the number of records. A tag exists at the end of a page and increases in a reverse order. gas number This value has the offset and the size of records, and 2 bytes are allotted for each. A record exists at the offset from the end of the page header, and its size is the same as Record Size. The first value in the tag area is not a tag that points to a real record, so analysis requires special attention.

Page types have been known so far, such as data, branch, empty, space tree, index, long value, and pages can be distinguished by page flag values. A record storage method is page-type dependent, and can be identified through analyzing data, branch, and long value pages. Data pages refers to a page in which real data of a table is recorded. A data page is in B-Tree structure and consists of a root page and a leaf page. 9gag nsfw A root page is the top page in the B-Tree structure, and the page number is represented as ColtypOrPgnoFDP when the type value is 1 in the catalog table. A leaf page is the bottom page in B-Tree structure. Leaf pages are structured as double-linked list, and in the header are previous and next page number. A branch page is a page where sub-page numbers are recorded in B-Tree structure. A long value page refers to a page used to save big data in the LV table.