You can use the RECOVER command to restabilize a database after a transaction is interrupted. The following conditions can interrupt a transaction:
•R:BASE discovers minor inconsistencies or unresolvable resource conflicts within a transaction. R:BASE automatically rolls back the transaction and displays an error message.
•Transaction processing has been interrupted unexpectedly. When you try to connect to the database, R:BASE detects either an existing Before Image file or major inconsistencies. An error message tells you to use the RECOVER command.
Other users connected to the same database might get the same message, but not until they disconnect from the database and try to reconnect to it. The transactions entered by other users still connected to the database are executed properly unless they try to access system resources (such as tables and views) that are directly affected by the transaction error.
When transaction processing is on, R:BASE creates Before Image files for the current database.
When you use the RECOVER command, it rolls back the interrupted transaction by using each Before Image file, clears all table and database locks, and resolves any other internal inconsistencies.
Before you run the recovery program, do the following:
•Backup your database and Before Image files.
•Make sure all users have exited from the affected database.
•Change to the directory that contains the affected database and Before Image files.
To use the recovery program:
| 1. | At the R> Prompt, enter RECOVER. All the databases that need to be recovered are listed. |
| 2. | At the R> Prompt, enter RECOVER dbname, where dbname is the name of the database you want to recover. |
| 3. | R:BASE displays a message recommending that you backup the damaged database and Before Image files. If you want to continue, select Yes. If you want to stop the RECOVER command to backup the necessary files, select No. |
| 4. | RECOVER displays the names of any damaged Before Image files and asks whether to delete them in order to recover the rest of the database. To delete these files, select Yes. To skip the deletion, select No. However, you must delete damaged Before Image files before you can access the database. |
RECOVER displays a list of any Before Image files it expects but cannot find. You can leave the database unrecovered, or recover it without the missing files. You cannot reconstruct a Before Image file.
A message is displayed when the recovery is complete. The recovery process removes all table and database locks that were active when processing was interrupted.
Transaction Processing Topics:
Locking Table Access and Resource Waiting
Row Locks and Transaction Processing
Automatic Table and Database Locks
Displaying Transaction Processing Locks
