Rebuilding "in-doubt" states reliably after multiple system failures in a data processing system performing two-phase transaction processing

A data processing node configured to participate in global transactions comprising:

• A) a transaction processing application operating within a global transaction processing protocol incorporating a two-phase commit procedure;
• B) coupling means to at least one other data processing node operating within the global transaction processing protocol for information exchange therewith;
• C) a memory storing database files subject to access during transaction processing;
• D) a database access application communicating with the transaction processing application to address files stored in the memory and transfer data between the transaction processing application and the memory;
• E) a file management system having exclusive access to reserved locations in the memory for reading and writing meta-data therein;
• F) physical file access logic selectively coupling the memory and the database access application, the physical file access logic incorporating file protections which are controlled by the file management system;
• and
• G) node recovery means for recovering following a system failure which occurs during transaction processing on a database stored in said memory and faithfully rebuilding, after restart, the data processing node to the state immediately prior to the failure;
• said node recovery means including:
• 1) means to remove the results of incomplete non-“in-doubt” transactions;
• 2) means to lock files which have been updated by “in-doubt” transactions;
• and
• 3) means for permitting normal access to the database after the operations carried out by the means set forth in subparagraphs G)1) and G)2) have completed.