Extensible Storage Engine (ESE), also known as JET Blue, is an ISAM (indexed sequential access method) data storage technology from Microsoft. ESE is the core of Microsoft Exchange Server, Active Directory, Branch Cache, and Windows Search. It's also used by a number of Windows components including Windows Update client and Help and Support Center. Its purpose is to allow applications to store and retrieve data via indexed and sequential access.

ESE provides transacted data update and retrieval. A crash recovery mechanism is provided so that data consistency is maintained even in the event of a system crash. Transactions in ESE are highly concurrent making ESE suitable for server applications. ESE caches data intelligently to ensure high performance access to data. In addition, ESE is lightweight making it suitable for auxiliary applications.

The ESE Runtime (ESENT.DLL) has shipped in every Windows release since Windows 2000, with native x64 version of the ESE runtime shipping with x64 versions of Windows XP and Windows Server 2003. Microsoft Exchange, up to Exchange 2003 shipped with only the 32-bit edition, as it was the only supported platform. With Exchange 2007, it ships with the 64-bit edition.

JET 蓝色最初是由 microsoft 开发的, 它是Microsoft Access中JET数据库引擎的潜在升级, 但从未在此角色中使用过。相反, 它继续被 Exchange 服务器、活动目录、文件复制服务(FRS)、安全配置编辑器、证书服务、 Windows Internet 名称服务(WINS) 和许多其他 Microsoft 服务使用,应用程序和 Windows 组件。 [7] 多年来, 它是 Microsoft 仅使用的专用 api, 但此后已成为任何人都可以使用的已发布 api。

1989年3月艾伦瑞特加入微软时, 数据访问引擎 (DAE) 开始工作。在接下来的一年里, 四开发团队为艾伦工作, 基本上完成了 ISAM。微软已经有了 BC7 ISAM (JET 红色), 但开始了数据访问引擎 (DAE) 的努力, 以建立一个更健壮的数据库引擎作为一个条目在随后的新的客户端-服务器体系结构领域。1990年春季, BC7 ISAM 和 DAE 团队加入成为联合发动机技术 (喷气) 的努力;负责生产两个引擎的 v1 (JET 红色) 和 v2 (jet 蓝色), 它将符合相同的 API 规范 (jet api)。大成喷气蓝色为以色列的旗子的颜色。BC7 ISAM 成为喷气机红色为旗子的颜色俄国。虽然喷气蓝和喷气红色被写了到同一 API 规格, 他们不分享 ISAM 代码任何。他们都支持一个共同的查询处理器, QJET, 后来连同 BC7 ISAM 成为与喷气红的同义词。

JET 蓝色首先在1994年作为 ISAM 在 Windows NT 3.5 中作为 WINS、DHCP 和现在已失效的RPL服务发送。它再次作为 Microsoft Exchange 的存储引擎在1996年再次发运。其他 windows 服务选择了 jet 蓝色作为其存储技术, 到 2000年, windows 的每个版本都开始以 jet 蓝色装运。JET 蓝色由活动目录使用, 并成为一组特殊的 Windows 代码 (称为可信计算基) (TCB) 的一部分。使用 jet 蓝色的 Microsoft 应用程序的数量继续增长, jet 蓝色 API 于2005年发布, 以方便 Windows 内外越来越多的应用程序和服务的使用。

While they share a common lineage, there are vast differences between JET Red and ESE.

• JET Red is a file sharing technology, while ESE is designed to be embedded in a server application, and does not share files.
• JET Red makes best effort file recovery, while ESE has write ahead logging and snapshot isolation for guaranteed crash recovery.
• JET Red before version 4.0 supports only page level locking, while ESE and JET Red version 4.0 supports record level locking.
• JET Red supports a wide variety of query interfaces, including ODBC and OLE DB. ESE does not ship with a query engine but instead relies on applications to write their own queries as C ISAM code.
• JET Red has a maximum database file size of 2 GiB, while ESE has a maximum database file size of 8 TiB with 4 KiB pages, and 16 TiB with 8 KiB pages.