Rhino Structure

  

Figure: The Rhino extension structure. The Rhino system consists of shaded regions. It uses the file system extensions for database I/O and logging, and the virtual memory extensions for database buffering. Rhino is used by UNIX applications linked with the transaction library.

The shaded regions of Figure 3 show the structure of Rhino. Persistent malloc and system call stubs are linked into applications as a library. The following additional components reside in the kernel address space as an extension.

• The transaction manager starts and terminates transactions.
• The storage manager is the core of Rhino. It detects applications' reads and writes and logs them to ensure the ACID property. It also manages buffers using memory objects.
• The log manager manages the log device, which is a sequential-write, random-read persistent device [gray]. It is used by the storage manager to guarantee database durability and atomicity. The log manager also coordinates crash recovery when Rhino is installed.

• The lock manager manages locks on regions. It also detects deadlocks.

Rhino uses several standard extensions to carry out operations. It stores databases and log records in files managed by file system extensions. Files are usually stored in the extent-based file system, which allocates files on contiguous blocks and does not cache blocks in memory. Rhino cooperates with the virtual memory extension to manage database buffers. Its buffer management is described in detail in Section 4.