Glosario de Bases de Datos Sybase, "E,F,G,H"

engine

An instance of the Adaptive Server executable that can communicate with other Adaptive Server engines in shared memory. An Adaptive Server running on a uniprocessor machine always has one engine, engine 0. An Adaptive Server running on a multiprocessor machine can have one or more engines. Also called server engine.

enterprise data

Data that exists anywhere in a networked system. Enterprise data can be stored on Sybase servers or as heterogeneous data.

entity

A database or a database object that can be identified by a unique ID and that is backed by database pages. Examples of entities are the database pubs2, the log for database pubs2, the clustered index for table titles in database pubs2, and the table authors in database pubs2. Identifying entities is the first step in the logical design of a database.

equijoin

A join based on equality.

error handling

Techniques available to Transact-SQL programmers on which to base code and display errors and error messages.

error log

A file that stores severe error message s and the results of the startup and recovery of databases.

error message

A message issued by Adaptive Server, usually to the user's terminal, when Adaptive Server detects an error condition.

error state number

The number attached to a Adaptive Server error message that allows unique identification of the line of Adaptive Server code at which the error was raised.

evaluated configuration

The configuration of SQL Server that was evaluated at the C2 security level by the NSA (National Security Agency) in 1996 on the HP 9000 HP-UX BLS, 9.09+ platform. Certain features of SQL Server, such as remote procedures and direct updates to system tables, were excluded from the evaluated configuration. For a complete list of features excluded from the evaluated configuration, see Appendix A in the SQL Server Installation and Configuration Guide for HP 9000 HP-UX BLS, 9.09+ .

exclusive lock

A type of lock acquired on an object during a write operation. It does not allow other transactions to acquire exclusive, updated, or shared locks on the object. Exclusive locks can be obtained on a table or page.

execute cursor

A cursor that is a subset of client cursors whose result set is defined by a stored procedure that has a single select statement. The stored procedure can use parameters. The values of the parameters are sent through Open Client calls.

existence join

A type of join performed in place of certain subqueries. Instead of the usual nested iteration through a table that returns all matching values, an existence join returns TRUE when it finds the first value and stops processing. If no matching value is found, it returns FALSE.

expression

A computation, column data, a built-in function, or a subquery that returns values.

Extended Stored Procedure (ESP)

A mechanism for calling external procedural language functions from within Adaptive Server. Users invoke an extended stored procedure using the same syntax as they use for a regular stored procedure, but instead of executing Transact-SQL statements, the ESP executes procedural language code, which is compiled in a dynamic link library (DLL) or shared library.

extent

Whenever a table or index requires space, Adaptive Server allocates a block of eight 2K pages, called an extent, to the object.

external login

An alternate login name and password used when a Component Integration Services client logs into a remote server. It is created using sp_addexternlogin.

fatal errors

Errors with severity levels of 19 and above. They terminate the user's work session, so that it is necessary to log in again.

fetch

A fetch moves the current cursor position down the cursor result set. Also called a cursor fetch.

field

See column .

FIPS flagger

An Adaptive Server option activated with the set command. When the Federal Information Processing Standards (FIPS) flagger is active, Adaptive Server returns a warning message when you use Transact-SQL extensions to entry level SQL92. FIPS recognizes SQL89 as the base standard.

foreign key

A key column in a table that logically depends on a primary key column in another table. Also, a column (or combination of columns) whose values are required to match a primary key in some other table.

format file

A file created while using bcp to copy data out from a table in a Adaptive Server database to an operating system file. The format file contains information on how the data being copied out is formatted and can be used to copy the data back into a Adaptive Server table or to perform additional copy outs.

fragment

When you allocate only a portion of the space on a device with create or alter database , that portion is called a fragment.

freelock list

On a multi-engine Adaptive Server, each engine has its own freelock list (a list of locks available to satisfy lock requests). If the engine freelock list runs out of locks, Adaptive Server moves locks from the global freelock list to the engine freelock list.

free-space threshold

A user-specified threshold that specifies the amount of space on a segment, and the action to be taken when the amount of space available on that segment is less than the specified space.

functions

See built-in functions .

gateway

Intermediate software that provides language translation, datatype conversion, and protocol conversion between the client and the data source.

Generic Access Module

A customer-built Open Server application used as a gateway. The application must conform to the interface described in the OmniSQL Server Generic Access Module Reference Manual. Customers are no longer encouraged to build applications to the generic access specification. The sds specification is preferred.

global variable

A system-defined variable that Adaptive Server updates on an ongoing basis. For example, @@error contains the last error number generated by the system. See also local variable .

group

A uniquely named set of users assigned a set of permissions for the objects and operations within a database.

grouped aggregate

See vector aggregate .

guest

A user name in the sysusers table of the model database, which enables a user with a valid Adaptive Server login to use databases created from model, with limited privileges.

Halloween problem

An anomaly associated with cursor updates, whereby a row seems to appear twice in the result set. This happens when the index key is updated by the client and the updated index row moves farther down in the result set.

hard fault

A persistent corruption of Adaptive Server found during a dbcc checkstorage operation. Hard faults cannot be correct by restarting Adaptive Server. See also soft fault .

hash-based access method

A category of parallel access method in which multiple worker processes work on a single chain of index or data pages. This category includes parallel hash-based table scan and parallel nonclustered index hash-based scan .

heap table

A table without a clustered index , where data is stored as a heap. The data rows are not stored in any particular order, and new data is always inserted on the last page of a page chain. A typical heap table is an unpartitioned table without a clustered index, but a partitioned table without a clustered index is also classified as a heap table.

heterogeneous data

Any data from non-Sybase data sources such as Oracle, Informix, or DB2.

hexadecimal string

A hexadecimal-encoded binary string that begins with the prefix 0x and can include the digits 0 through 9 and the uppercase and lowercase letters A through F. The interpretation of hexadecimal strings is platform specific. For some systems, the first byte after the prefix is the most significant; for others, the last byte. For example, the string 0x0100 is interpreted as 1 on some systems and as 256 on others.