Log Manager

The Logging Protocol for Minibase is based on ARIES. It uses WAL (write-ahead logging), and it supports the use of the Steal/No-force policy by the Buffer Manager.

Design Decisions

The Log Manager does a physical logging of all changes to the database. It has no knowledge of log record types and merely interprets log records as sequences of bytes. It primarily interacts with the Recovery Manager.

The log record is maintained as a UNIX file. All updates are performed through the Recovery Manager into the log tail. Writes to the log are sequential. The log tail is stored in shared memory, and is a derived class of the base SharedRegion class i.e. a semaphore guards access to the log tail.

The Log Manager defines the structure of the log sequence number (LSN). Every log record has a distinct LSN. In the case of Minibase, the LSN is merely the offset from the beginning of the log. The value of the LSN is assigned by the Recovery Manager.

Click here for the public interface. Click here for more details.

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