Adabas Concurrency check

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# Adabas Concurrency check

Adabas databases can be addressed from different environments, define the same directory for the storage. This would destroy the integrity of the database. Therefore, it should be avoided.

## Locking Mechanism

Adabas implements a locking mechanism designed to safeguard an Adabas database against multiple usage in different database processes. This mechanism utilizes a special lock file to indicate that a database is already in use and should not be reused in a different adanuc process.

## Locking Workflow

The handling of the locking mechanism starts directly at database start. The nucleus checks the accessibility of the lock file directly at the beginning. The existence of this lock file already indicates ownership of the database. This file consists of the process id and the computer name of its creator process. With this information the nucleus process then tries to figure out if the ownership could be taken over. This is only then possible, if the computer name is the same as the local host name and the process does not exist any longer. Otherwise, the nucleus refuses to start and drops an error message.

## Lock File

The lock file will be placed at the location of the ASSO1 file. It contains the local host name and the process id for identification, delimited by a semicolon. The file name is predefined to _DB_LOCK, which should then show up as the first file for the user (if sort ascending is set) and acts as an eye-catcher.

## Troubleshooting

Manual intervention is an option in any case of trouble. The lock file can be removed manually if the database is locked by accident. Please ensure the database is not used by any other process in the network.

### On this page

- Locking Mechanism
- Locking Workflow
- Lock File
- Troubleshooting