Preserving the appropriate amount of space within log file, permanent store file, and temporary store file of a file store helps to ensure that operations and transactions behave predictably.
Data is first written to the log file sequentially, that is, new records are added to the end of the file. When the end of the log file is reached, old records at the beginning of the log file are overwritten by new records and this process repeats. Subsequently, data is written to the permanent store file and temporary store file. The exception is extremely short-lived data, which is only written to the log file.
The permanent store file and temporary store file each have a minimum reserved size and a maximum size. When they are created, the permanent and temporary store files consume their minimum reserved sizes, plus the size of the log. If the maximum size is set to a larger value than the minimum reserved size, the files grow up to the maximum size as required.
The default settings for the minimum and maximum sizes are most suitable if you are not using a dedicated disk for your file store because they protect the file store from other disk users, and also protect other disk users from the file store. The default settings are less appropriate if you have a disk that is dedicated to file store use, and in this case you might want to consider setting the maximum size set to unlimited.
If your file store is not on a dedicated disk, consider making the minimum and maximum sizes the same. Initially, the message store reserves the amount of space defined by the minimum setting. Therefore, if you use the same value for the maximum and minimum settings, this reduces the likelihood of other applications using disk space that you had intended for file store use. Setting the maximum size to a value other than unlimited reduces the likelihood of the file store using disk space that you had intended for use by other applications. Other applications can include, for example, the application server itself.
The default configuration for file store attributes is intended to be sufficient to be used in typical messaging workloads without any administration. To improve the performance or availability of the log or the two store files, the administrator can modify the file store attributes to control where these files are placed. Similarly, the administrator can modify the attributes which control the sizes of the log and two store files to handle workloads with a large number of active transactions, large messages or a large volume of message data resident in the messaging engine.
The following table shows the minimum and default values for file store attributes.
Name | Description | Minimum and Default Values in mega bytes |
---|---|---|
Log size | Size of the log file, in mega bytes |
|
Minimum permanent store size | The minimum number of mega bytes reserved by
the permanent store file. Note: The minimum store file size must always
be at least as big as the log file size.
|
|
Maximum permanent store size | The maximum size in mega bytes of the permanent
store file. Note: Consider making the maximum store
file size double the size of the log file. The maximum size of the
store file must always be larger than the log file. If the log file
size is the same as the maximum store file size then the messaging
engine will not start.
|
|
Minimum temporary store size | The minimum number of mega bytes reserved by
the temporary store file. Note: The minimum store file size must always
be at least as big as the log file size.
|
|
Maximum temporary store size | The maximum size in mega bytes of the temporary
store file. Note: Consider making the maximum store file
size double the size of the log file. The maximum size of the store
file must always be larger than the log file. If the log file size
is the same as the maximum store file size then the messaging engine
will not start.
|
|
Unlimited permanent store size | Indicates whether the permanent store file is unlimited in size |
|
Unlimited temporary store size | Indicates whether the temporary store file is unlimited in size |
|
Log directory | Name of the directory that the log file is in |
|
Permanent store directory | Name of the permanent store file's directory |
|
Temporary store directory | Name of the temporary store file's directory |
|