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# JMS Server: Configuration: Thresholds and Quotas

Configuration Options Related Tasks Related Topics

Use this page to define thresholds, which trigger this JMS server to carry out events such as generating log messages, and quotas, which specify maximums for memory use, message size and number of messages available to this JMS server.

#### Configuration Options

Name | Description
--- | ---
Bytes Maximum | The maximum number of bytes that can be stored in this JMS server. A value of `-1` removes any WebLogic Server limits. Because excessive bytes volume can cause memory saturation, BEA recommends that this maximum corresponds to the total amount of system memory available after accounting for the rest of your application load. Range of Values: >= BytesThresholdHigh MBean Attribute: `JMSServerMBean.BytesMaximum` Minimum value: `-1` Maximum value: `9223372036854775807`
Bytes Threshold High | The upper threshold (number of bytes stored in this JMS server) that triggers flow control and logging events. A value of `-1` disables the events for this JMS server. The triggered events are: `Log Messages` - A message is logged on the server indicating a high threshold condition. `Flow Control` - If flow control is enabled, the JMS server becomes armed and instructs producers to begin decreasing their message flow. Range of Values: <= BytesMaximum; >= BytesThresholdLow MBean Attribute: `JMSServerMBean.BytesThresholdHigh` Minimum value: `-1` Maximum value: `9223372036854775807`
Bytes Threshold Low | The lower threshold (number of bytes stored in this JMS server) that triggers flow control and logging events. A value of `-1` disables the events for this 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. `Flow Control` - If flow control is enabled, the JMS server becomes disarmed and instructs producers to begin increasing their message flow. Range of Values: <= BytesThresholdHigh MBean Attribute: `JMSServerMBean.BytesThresholdLow` Minimum value: `-1` Maximum value: `9223372036854775807`
Messages Maximum | The maximum number of messages that can be stored in this JMS server. A value of `-1` removes any WebLogic Server limits. Because excessive message volume can cause memory saturation, BEA recommends that this value corresponds to the total amount of system memory available after accounting for the rest of your application load. Range of Values: >= MessagesThresholdHigh. MBean Attribute: `JMSServerMBean.MessagesMaximum` Minimum value: `-1` Maximum value: `9223372036854775807`
Messages Threshold High | The upper threshold (number of messages stored in this JMS server) that triggers flow control and logging events. A value of `-1` disables the events for this 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. `Flow Control` - If flow control is enabled, the JMS server becomes armed and instructs producers to begin decreasing their message flow. Range of Values: <= MessagesMaximum; >= MessagesThresholdLow. MBean Attribute: `JMSServerMBean.MessagesThresholdHigh` Minimum value: `-1` Maximum value: `9223372036854775807`
Messages Threshold Low | The lower threshold (number of messages stored in this JMS server) that triggers flow control and logging events. A value of `-1` disables the events for this 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. `Flow Control` - If flow control is enabled, the JMS server becomes disarmed and instructs producers to begin increasing their message flow. Note: This attribute is dynamically configurable. Range of Values: <= MessagesThresholdHigh MBean Attribute: `JMSServerMBean.MessagesThresholdLow` Minimum value: `-1` Maximum value: `9223372036854775807`
Maximum Message Size | The maximum number of bytes allowed in individual messages on this JMS server. The size of a message includes the message body, any user-defined properties, and the user-defined JMS header fields `JMSCorrelationID` and `JMSType`. 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. Note: Any change to this maximum affects only incoming messages; stored messages are not affected. MBean Attribute: `JMSServerMBean.MaximumMessageSize` Minimum value: `0` Maximum value: `2147483647`
Blocking Send Policy | Determines whether the JMS server delivers smaller messages before larger ones when a destination has exceeded its maximum number of messages. `FIFO` prevents the JMS server from delivering smaller messages when larger ones are already waiting for space. `Preemptive` allows smaller send requests to preempt previous larger ones when there is sufficient space for smaller messages on the destination. This policy is defined only for the JMS server; it cannot be set on individual destinations. Additional information on the `FIFO` and `Preemptive` policies is provided below. `FIFO` (first in, first out) 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. If there is sufficient space for a given request, then that request is completed and the next request is considered. If there is insufficient space for a given request, then no further requests are considered until sufficient space becomes available for the current request to complete. `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. If there is sufficient space for a given request, then that request is allowed to continue and the next request is considered. If there is insufficient space for a given request, then that request is skipped and the next request is considered. MBean Attribute: `JMSServerMBean.BlockingSendPolicy`

Related Tasks

- Configure JMS system modules
- Configure queue thresholds and quota
- Configure topic thresholds and quota

Related Topics

- Configuring and Managing WebLogic JMS
- Programming WebLogic JMS