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Keeping a Database Directory Synchronous With the Databases on the File System for the Os/2 Database Manager

IP.com Disclosure Number: IPCOM000034912D
Original Publication Date: 1989-May-01
Included in the Prior Art Database: 2005-Jan-27
Document File: 2 page(s) / 14K

Publishing Venue

IBM

Related People

Devany, EP: AUTHOR [+3]

Abstract

Disclosed is a method to assure that the database directory information is accurate, regardless of errors caused by system crashes due to power failures or other disasters. The Database Manager maintains a directory that cross references all databases accessed from a user's computer system. Before issuing transactions with a database, the user must logically connect to the database. The database is located through the database directory which cross references the database name with the node, drive and subdirectory containing the database files. If the database directory information is not accurate, the user cannot connect to the database to reference the data that was stored there. When a new database is created, this cross reference information is placed in the database directory.

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Keeping a Database Directory Synchronous With the Databases on the File System for the Os/2 Database Manager

Disclosed is a method to assure that the database directory information is accurate, regardless of errors caused by system crashes due to power failures or other disasters. The Database Manager maintains a directory that cross references all databases accessed from a user's computer system. Before issuing transactions with a database, the user must logically connect to the database. The database is located through the database directory which cross references the database name with the node, drive and subdirectory containing the database files. If the database directory information is not accurate, the user cannot connect to the database to reference the data that was stored there. When a new database is created, this cross reference information is placed in the database directory. If a new database is being created when the computer system loses power, or a similar catastrophy causing the processor to stop before completion of the create, the database directory information would be out of sync with the databases on the system. For example, the subdirectory and database files were created, but processing stopped before the directory entry was made for the new database. Similarly, if a database is to be dropped, the processor could stop before the database directory is updated and cause the directory information to be out of sync with the databases on the system. The naming convention used by the Database Manager and the method used for creating database files and directories will, in most cases, prevent further creation of databases after a system 'crash'. To prevent this problem, an 'intention' file is created along with the primary and backup directory files when the first database is created on a computer system's fixed disk or diskette drive. The intention file is used to record the next operation to be performed. The record of the next operation is written to the intention file before the operation begins. If the system 'crashes' before the operation completes, the Database Manager has a record of the activity at the time of the crash and uses this information to clean up the directory and/or the database files. The following examples show how the intention file is used. When a database is created, the database directory is OPE...