Product Documentation

FairCom ISAM for C

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FairCom's transaction management system maintains files that record various states of information necessary to recover from unexpected problems. Information concerning ongoing transactions is saved on a continual basis in these transaction log files. A chronological series of transaction logs is maintained during the operation of the application. Transaction logs containing the actual transaction information are saved as standard files. They are given names in sequential order, starting with L0000001.FCS (which can be thought of as active transaction log, number 0000001) and counting up sequentially (that is, the next log file is L0000002.FCS, etc.).

By default, the transaction management logic saves up to four active logs at a given time. When there are already four active log files and another is created, the lowest numbered active log is either deleted or saved as an inactive transaction log file, depending on how FairCom DB is configured.

Every new FairCom Server session begins with checking the most recent transaction logs (the most recent 4 logs, which are always saved as “active” transaction logs) to determine if any transactions need to be undone or redone. If so, these logs are used to perform automatic recovery.

The FairCom DB transaction logs serve as the ultimate control point for many important FairCom DB features:

  • Automatic Recovery on startup
  • Dynamic Backups
  • Roll forward/backward capabilities
  • Replication
  • Change History