Gustav Brock
Gustav at cactus.dk
Sun Apr 2 03:48:45 CDT 2006
Hi Marty Thanks for pointing this out! Today I learned that JET means Joint Engine Technology ... However, I would be careful stating that AD/Exchange and Access use the "same" engine as this "same" seems to assume a state prior to 1990: http://msdn.microsoft.com/library/default.asp?url=/library/en-us/ese/ese/extensible_storage_engine_errors.asp <quote> The Extensible Storage Engine (ESE) was formerly known as JET Blue, and so frequently the term "JET Blue" or "JET" is used interchangeably with ESE. However, there are in fact two completely separate implementations of the Joint Engine Technology (JET) API, called JET Blue and JET Red. The term "JET" is frequently also used to refer to JET Red, which is the database engine under Microsoft Office Access. The two JET implementations are completely different, are separately maintained, have a vastly different feature set, and are not interchangeable. .. </quote> /gustav >>> martyconnelly at shaw.ca 01-04-2006 23:16:04 >>> Someone asked me for a counter argument regarding the use of Jet and by default Access. So here is something I pieced together from some blogs, I can't remember seeing anything posted here on Jet version's Red and Blue. Most of these database types have good arguments against using JET but don't realize that Active Directory Services and Exchange are built on top of JET. Don't tell me, they would throw out these applications because of their prejudices. Yes, Mr CIO, I know, but we have to get rid of all those Active Directory Services that you just spent two years installing because Gasp! it's based on a JET database engine. I really like bringing this up to the one trick pony Oracle types who work on Windows. It is fun to watch them squirm for awhile; although a knowledgeable db type can counter this. So here is some info to throw at them. JET was originally part of Access (or FoxPro for some of the very early MS versions). It split into Jet Red and Jet Blue. Jet Blue was used for MSExchange and Active Directory and is shipped with Windows 2000 and later. It's now known as ESE. Jet Red was still shipped with Access. All throughout it's history, Jet Red has been freely distributable. Many many many VB apps were shipped with Jet Red. JET Red was an ISAM originally developed by Microsoft for BC7, compiled basic. JET Blue was originally developed by Microsoft as a prospective upgrade for Access, but it was never used in this role. JET Red and JET Blue began sharing the common JET moniker in the Spring of 1990 when a query technology, QJET, was developed that would host on both Red and Blue. JET Blue went on to be used by Microsoft Exchange, Active Directory and many many other Windows services. JET Blue was a private API for many years, but became a published API in April of 2005 when three middle ware applications not covered by the Windows EULA chose it as their data store. Now anyone can use JET Blue. Extensible Storage Engine (ESE) -- the Active Directory database engine. ESE (Esent.dll) is an improved version of the Jet database that is used in Microsoft Exchange Server versions 4.x and 5.5. It implements a transacted database system, which means that it uses log files to ensure that committed transactions are safe. The ESE engine used by Active Directory is based on Microsoft's Jet database technology. Jet uses a b-tree file structure with transaction logs to ensure recoverability in the event of a system or drive failure. JET Red is a file sharing technology with page level locking and best effort crash recovery. JET Blue on the other hand is designed to be embedded in a server application, does not share files, has write ahead logging for guaranteed crash recovery and has record level locking. JET Blue does not ship with a query engine but instead relies on applications to write their own queries as C++ ISAM code. With the release of Access 12 the Jet Red development team has been split off from it's old SQL Server department and is free to develop on it's own. Extensible Storage Engine API's http://msdn.microsoft.com/library/default.asp?url=/library/en-us/ese/ese/extensible_storage_engine_errors.asp Access 12's new data engine ACEDB http://blogs.msdn.com/access/archive/2005/10/13/480870.aspx -- Marty Connelly Victoria, B.C. Canada