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WebLogic Server Configuration Reference

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JMSFileStore

 

Description

This class represents a JMS file-based persistent store.

 

Syntax

<JMSFileStore
  Directory="String"
  Name="String"
  Notes="String"
  SynchronousWritePolicy=( "Disabled" | "Cache-Flush" | "Direct-Write" )
/>

 

Parent Elements

 

Attributes

Table 28-1 JMSFileStore attributes

Attribute

Description

Range of Values and Default

Directory

Defines the directory where the file-based persistent store exists.

This attribute is not dynamically configurable.

Admin Console field label: Directory

Name

The name of this configuration. WebLogic Server uses an MBean to implement and persist the configuration.

Admin Console field label: Name

Required: no

Notes

Optional information that you can include to describe this configuration.

Admin Console field label: Notes

Required: no

SynchronousWritePolicy

The WebLogic JMS file store provides three synchronous write policies: Disabled, Cache-Flush, and Direct-Write. These policies configure how the file store writes data to disk, and affect performance, scalability, and reliability.

Disabled -- File store writes are allowed to use both the operating system's cache as well as the file system's on-disk cache. This policy is the fastest, but the least reliable. It can be more than 100 times faster than the other policies, but power outages or operating system failures can cause lost and/or duplicate messages.

Cache-Flush -- The default policy. Transactions cannot complete until all of their writes have been flushed down to disk. This policy is reliable and scales well as the number of simultaneous users increases.

Direct-Write -- File store writes are written directly to disk. This policy is supported on Solaris, HP, and Windows. If this policy is set on an unsupported platform, the file store automatically uses the Cache-Flush policy instead. The Direct-Write policy's reliability and performance depend on operating system and hardware support of on-disk caches, as follows:


  • With on-disk caching enabled, the Direct-Write policy can be 2-5 times faster than the Cache-Flush policy, except in highly scalable cases where it may be slightly slower.

  • With on-disk caching disabled, the Direct-Write policy is faster than the Cache-Flush policy in one-to-many cases, but is much slower otherwise.

  • The Direct-Write policy scales well with on-disk caching enabled, but does not scale with it disabled. (Solaris does not allow enabling the on-disk cache for direct writes).

Warning! Unlike Solaris and HP, use of the Direct-Write policy on Windows may leave transaction data in the on-disk cache without writing it to disk immediately. This is not transactionally safe (i.e., not reliable), since a power failure can cause loss of on-disk cache data-- possibly resulting in lost and/or duplicate messages. For reliable writes using Direct-Write on Windows, either disable all write caching for the disk (enabled by default), or use a disk with a battery backed cache.

To disable the on-disk cache for a hard drive on Windows:
Start -> Settings -> Control Panel -> System -> Hardware tab -> Device Manager button -> Disk Drives -> double-click drive name -> Disk Properties tab -> deselect "Write Cache Enabled" check box. Some file systems do not allow this value to be changed (for example, a RAID system that has a reliable cache).

Note: If the JMS file store is used exclusively for paging non-persistent messages to disk, the synchronous write policy is ignored.

Admin Console field label: Synchronous Write Policy

Required: no

Default: Cache-Flush

 

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