了解Oracle内核代码层的作用

最新推荐文章于 2025-08-11 14:58:53 发布

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原文链接：https://yq.aliyun.com/articles/524159

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#数据库

本文详细介绍了Oracle RDBMS内核的多层架构及其关键组件，包括缓存层KC、事务层KT、递归程序接口RPI、行缓存层等。这些组件共同实现了Oracle的空间管理功能。

Oracle RDBMS Kernel 的代码分成多层次，如<Oracle8i Internal Services>一书所介绍的：

其中部分代码层的作用: The cache layer (KC)

The cache layer manages the database buffer cache. It uses operating system dependent facilities for data file I/O, provides concurrency control facilities for local access to the cache buffers, and provides parallel cache management (PCM) instance locking facilities for Oracle parallel server. The other main responsibility of the cache layer is the control of redo generation into the log buffer, and the writing of redo to the log files. The cache layer also caches control file information.

To read blocks.
To update blocks in redo only mode.

The transaction layer (KT)

This layer is responsible for the allocation of transactions to rollback segments, interested transaction list changes within data blocks, changes to rollback segment blocks for undo generation, transaction control facilities such as savepoints, and read consistency. The transaction layer is also responsible for space management, both at the level of segment free lists and at the level of tablespace extent allocation.

To update blocks with undo.
To check with the status of the transaction.
To manage recursive transactions for nested space operations.

The recursive program interface (RPI)

The recursive program interface is used to populate the dictionary cache from the data dictionary. Row cache recursive SQL statements are executed in a separate call context, but are not parsed and optimized in the compilation layer.

Row Cache Layer