GT.M Database Basics (from iothrash utility manual)

GT.M Database Engine Basics

Database engines typically operate on two types of files . database files and journal files. In the case of GT.M, update information is written sequentially to the end of journal files to harden or commit transactions. Once an update is written to a journal file, it is considered recoverable and updates to the database can follow subsequently.

The GT.M database engine is daemonless. Processes run as normal user processes, and cooperate to manage the database. The logic resides in a shared library provided by GT.M that the processes link dynamically. Thus, any process can read or write any database file to which it has access permissions, and any process can append to journal files based on access permissions. In a small application, there are frequently tens of concurrently active processes; in a large application, there can be thousands of active processes concurrently accessing the same database and journal files.