Progress
Database Administration
Guide and Reference
Progress Database Architecture
The three Progress Version 9 databases (Enterprise, Workgroup, and Personal) contain not only data but also information about their schema. Figure 1–1 illustrates the components of a Progress Version 9 Database.
Figure 1–1: Version 9 Structure
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As shown in Figure 1–1, a typical Progress Version 9 database consists of:
- A structure description (.st) file, which defines the database’s structure. The .st file is a text file with an .st filename extension. The administration utility PROSTRCT CREATE uses the information in the .st file to create the database’s areas and extents. See "Creating and Deleting Databases," for detailed information about structure description files.
- An event log file, which is a text file with a .lg filename extension. The .lg file contains a history of significant database events, such as startup and shutdown.
- One database (.db) control area, which contains a database structure extent (a binary file with a .db filename extension). The control area and its .db file act as a table of contents, for the database engine, listing the name and location of every area and extent in the database.
- One primary recovery (before image) area, which contains one or more extents with a .bn filename extension. The .bi file stores notes about data changes. In the event of hardware failure, the database engine uses these notes to undo any incomplete transactions and maintain data integrity.
- One schema area, which contains at least one variable-length extent with a .dn filename extension. The schema area contains the master and sequence blocks, as well as schema tables and indexes. If no application data areas are created, the schema area contains all user data.
- Optionally, one transaction log (.tl) area when two-phase commit is in use. It contains one or more fixed-length extents with the .tn filename extension; variable-length extents are not allowed. The transaction log lists committed two-phase commit transactions.
NOTE: After-imaging is only available on the Progress Enterprise database.- Optionally, one after-image (.ai) area when after-imaging is enabled. The after-image area can contain many fixed-length extents and/or one variable-length extent with the .an filename extension. In the event of hardware failure, the database engine uses the .ai file and the most recent backup to reconstruct the database.
- Optionally, one or more application data areas each containing extents with the .dn filename extension. Application data areas contain tables, indexes, and other objects.
NOTE: Throughout this guide, the word database means collectively, the database, event log, transaction log, schema files and recovery files. You should treat these files as an indivisible unit. For example, the phrase “back up the database” means “back up the database data, .lg, .dn, .tl, .ai, and .bi files together.” This is an important concept to remember as you read through this guide.
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