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# JMS Server --> Configuration --> Thresholds & Quotas

Tasks Related Topics Attributes

## Overview

This tab defines threshold and quota attributes for an instance of a JMS server. A JMS server manages connections and message requests on behalf of clients. You must first configure a JMS server before you can configure any destinations or consumers.

## Tasks

Configuring a JMS Server

Targeting and Deploying a JMS Server

## Related Topics

"Managing WebLogic JMS" in Programming WebLogic JMS

## Attributes

Table 9-1

Attribute Label | Description | Value Constraints
--- | --- | ---
Bytes Maximum | The maximum bytes quota (total amount of bytes) that can be stored in this JMS server. The default value of -1 specifies that there is no WebLogic-imposed limit on the number of bytes that can be stored. However, excessive bytes volume can cause memory saturation, so this value should correspond to the total amount of available system memory relative to the rest of your application load. This attribute is dynamically configurable. Range of Values: >= BytesThresholdHigh MBean: `weblogic.management. configuration. JMSServerMBean` Attribute: `BytesMaximum` | Minimum: -1 Maximum: 9223372036854775807 Default: -1 Dynamic: yes
Bytes Threshold High | The upper threshold value that triggers events based on the number of bytes stored in the JMS server. If the number of bytes exceeds this threshold, the triggered events are: Log Messages - A message is logged on the server indicating a high threshold condition. Bytes Paging - If bytes paging is enabled (and a paging store has been configured), then server bytes paging is started. Flow Control - If flow control is enabled, the JMS server becomes armed and instructs producers to begin decreasing their message flow. This attribute is dynamically configurable. A value of -1 specifies that server bytes paging, flow control, and threshold log messages are disabled for the JMS server. Range of Values: <= BytesMaximum; >BytesThresholdLow Note: Bytes paging cannot be dynamically disabled by resetting the BytesThresholdHigh to -1. To disable paging, you could set the BytesThresholdHigh to a very large number, so that paging would not be triggered. MBean: `weblogic.management. configuration. JMSServerMBean` Attribute: `BytesThresholdHigh` | Minimum: -1 Maximum: 9223372036854775807 Default: -1 Dynamic: yes
Bytes Threshold Low | The lower threshold value that triggers events based on the number of bytes stored in the JMS server. If the number of bytes falls below this threshold, the triggered events are: Log Messages - A message is logged on the server indicating that the threshold condition has cleared. Bytes Paging - If bytes paging is enabled, paging is stopped (if paging is occurring). Flow Control - If flow control is enabled, the JMS server becomes disarmed and instructs producers to begin increasing their message flow. This attribute is dynamically configurable. A value of -1 specifies that server bytes paging, flow control, and threshold log messages are disabled for the JMS server. Range of Values: < BytesThresholdHigh MBean: `weblogic.management. configuration. JMSServerMBean` Attribute: `BytesThresholdLow` | Minimum: -1 Maximum: 9223372036854775807 Default: -1 Dynamic: yes
Bytes Paging Enabled | Specifies whether bytes paging is enabled on this JMS server for temporarily swapping message bodies out from memory when the JMS servers's byte load reaches a specified threshold. false - Server bytes paging is explicitly disabled. true - If a paging store has been configured, and both the BytesThresholdLow and BytesThresholdHigh values are greater than -1, then server bytes paging is enabled. If either the BytesThresholdLow or BytesThresholdHigh attribute is undefined, or defined as -1, then server bytes paging is implicitly disabled--even though this flag is set to true. MBean: `weblogic.management. configuration. JMSServerMBean` Attribute: `BytesPagingEnabled` | Default: false Valid values: true false
Messages Maximum | The maximum message quota (total amount of messages) that can be stored in this JMS server. The default value of -1 specifies that there is no WebLogic-imposed limit on the number of messages that can be stored. However, excessive message volume can cause memory saturation, so this value should correspond to the total amount of available system memory relative to the rest of your application load. This attribute is dynamically configurable. Range of Values: >= MessagesThresholdHigh MBean: `weblogic.management. configuration. JMSServerMBean` Attribute: `MessagesMaximum` | Minimum: -1 Maximum: 9223372036854775807 Default: -1 Dynamic: yes
Messages Threshold High | The upper threshold value that triggers events based on the number of messages stored in the JMS server. If the number of messages exceeds this threshold, the triggered events are: Log Messages - A message is logged on the server indicating a high threshold condition. Bytes Paging - If messages paging is enabled (and a paging store has been configured), then server messages paging is started. Flow Control - If flow control is enabled, the JMS server becomes armed and instructs producers to begin decreasing their message flow. This attribute is dynamically configurable. A value of -1 specifies that server messages paging, flow control, and threshold log messages are disabled for the JMS server. Range of Values: <= MessagesMaximum; >MessagesThresholdLow Note: Messages paging cannot be dynamically disabled by resetting the MessagesThresholdHigh to -1. To disable paging, you could set the MessagesThresholdHigh to a very large number, so that paging would not be triggered. MBean: `weblogic.management. configuration. JMSServerMBean` Attribute: `MessagesThresholdHigh` | Minimum: -1 Maximum: 9223372036854775807 Default: -1 Dynamic: yes
Messages Threshold Low | The lower threshold value that triggers events based on the number of messages stored in the JMS server. If the number of messages falls below this threshold, the triggered events are: Log Messages - A message is logged on the server indicating that the threshold condition has cleared. Bytes Paging - If messages paging is enabled, paging is stopped (if paging is occurring). Flow Control - If flow control is enabled, the JMS server becomes disarmed and instructs producers to begin increasing their message flow. This attribute is dynamically configurable. A value of -1 specifies that server messages paging, flow control, and threshold log messages are disabled for the JMS server. Range of Values: < MessagesThresholdHigh MBean: `weblogic.management. configuration. JMSServerMBean` Attribute: `MessagesThresholdLow` | Minimum: -1 Maximum: 9223372036854775807 Default: -1 Dynamic: yes
Messages Paging Enabled | Specifies whether messages paging is enabled on this JMS server for temporarily swapping message bodies out from memory when the JMS servers's message load reaches a specified threshold. false - Server bytes paging is explicitly disabled. true - If a paging store has been configured, and both the MessagesThresholdLow and MessagesThresholdHigh values are greater than -1, then server messages paging is enabled. If either the MessagesThresholdLow or MessagesThresholdHigh attribute is undefined, or defined as -1, then server messages paging is implicitly disabled--even though this flag is set to true. MBean: `weblogic.management. configuration. JMSServerMBean` Attribute: `MessagesPagingEnabled` | Default: false Valid values: true false
Maximum Message Size | The maximum size of a message that will be accepted from producers on this JMS server. The message size includes the message body, any user-defined properties, and the user-defined JMS header fields: `JMSCorrelationID` and `JMSType`. Producers sending messages that exceed the configured maximum message size for the JMS server will receive a `ResourceAllocationException`. The maximum message size is only enforced for the initial production of a message. Messages that are redirected to an error destination or forwarded to a member of a distributed destination are not checked for size. For instance, if a destination and its corresponding error destination are configured with a maximum message size of 128K bytes and 64K bytes, respectively, a message of 96K bytes could be redirected to the error destination (even though it exceeds the 64K byte maximum), but a producer could not directly send the 96K byte message to the error destination. This attribute is dynamically configurable, but only incoming messages are impacted; stored messages are not impacted. MBean: `weblogic.management. configuration. JMSServerMBean` Attribute: `MaximumMessageSize` | Minimum: 0 Maximum: 2147483647 Default: 2147483647 Dynamic: yes
Blocking Send Policy | The JMS server's policy on whether to deliver smaller messages before larger ones when a destination has exceeded its message quota. This can occur when multiple senders are competing for space on the same JMS server. This policy is defined only for the JMS server; it cannot be set on individual destinations. Valid expiration policies are: FIFO - The first in, first out policy indicates that all send requests for the same destination are queued up one behind the other until space is available. No send request is permitted to successfully complete if there is another send request waiting for space before it. When space is limited, the FIFO policy prevents the starvation of larger requests because smaller requests cannot continuously use the remaining available space. Smaller requests are delayed, though not starved, until the larger request can be completed. When space does become available, requests are considered in the order in which they were made. Preemptive - Indicates that a send operation can preempt other blocking send operations if space is available. That is, if there is sufficient space for the current request, then that space is used even if there are other requests waiting for space. When space is limited, the Preemptive policy can result in the starvation of larger requests. For example, if there is insufficient available space for a large request, then it is queued up behind other existing requests. When space does become available, all requests are considered in the order in which they were originally made. MBean: `weblogic.management. configuration. JMSServerMBean` Attribute: `BlockingSendPolicy` | Default: FIFO Valid values: FIFO Preemptive Dynamic: yes