File stores

File stores enable messaging engines to preserve operating information and to persist those objects that messaging engines need for recovery in the event of a failure, using a file system.

A file store is a type of message store that directly uses files in a file system through the operating system. File store mechanisms split data storage into three levels: the log file, permanent store files, and temporary store files.

Figure 1. The relationship between a messaging engine and its file store.
A messaging engine uses a JDBC data source to manage the interaction with a data store, which is held in a database
[Updated in December 2011]
Log file
This file contains information about currently active transactions and data that is not yet written to a store file. It is a circular log and its file size is static while a messaging engine is running, but can be changed if required. A restart of the messaging engine is required for the changes to take effect. The size of the log file limits the maximum size of a message that can be sent.
Permanent store file
This file contains permanent data that is retained after the restart of the messaging engine, such as persistent messages, queue data, and information about the storage and transmission of persistent messages.
The permanent store file can be configured to have a maximum and minimum size, or to be unlimited in size. The file can grow from the minimum size (or as required in the unlimited case) but will never shrink (even if the maximum size is set lower than its current size). The file sizes can be changed in the administration console, but a restart of the messaging engine is required for the changes to take effect.
Similar to a file system, when data is deleted from the store, the data in the file is not deleted, only the directory information is updated. This means that if a message is consumed, the message data may still be present in the store file, but the directory information that includes this data in the store is updated to reflect the fact that it is deleted.
Temporary store file
This file contains temporary data that is not retained after the restart of the messaging engine, such as nonpersistent messages that were spilled to the file store to release memory from the JVM heap. The temporary store file contents are truncated when the messaging engine starts.
The temporary store file can be configured to have a maximum and minimum size, or to be unlimited in size. The file can grow from the minimum size (or as required in the unlimited case) but will never shrink (even if the maximum size is set lower than its current size). The file sizes can be changed in the administration console, but a restart of the messaging engine is required for the changes to take effect.
Similar to a file system, when data is deleted from the store, the data in the file is not deleted, only the directory information is updated. This means that if a message is consumed, the message data may still be present in the store file, but the directory information that includes this data in the store is updated to reflect the fact that it is deleted.
[Updated in December 2011]
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[Updated in December 2011] You can configure where the file store files must be placed. By default, the file store uses a subdirectory in the following path: ${USER_INSTALL_ROOT}/filestores/com.ibm.ws.sib/${ME_NAME}. The file store directory contains two other directories; the log directory that contains the log file and the store directory that contains both the PermanentStore and TemporaryStore files. [Updated in December 2011]

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Subtopics
Hints and tips for configuring file store size
Related concepts
Learning about file stores
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