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Orchestrations are executable business processes that can subscribe to (receive) and publish (send) messages through the MessageBox database. In addition, orchestrations can construct new messages. Messages are received using the subscription and routing infrastructure.

When subscriptions are filled for orchestrations, a new instance is activated and the message is delivered, or in the case of instance subscriptions, the instance is rehydrated if necessary and the message is then delivered. When messages are sent from an orchestration, they are published to the MessageBox in the same manner as a message arriving on a receive location with the appropriate properties getting inserted into the database for use in routing.

Messages that are constructed in an orchestration must be placed in the MessageBox database and referenced by the orchestration instance, but they should not be published because they have not yet been sent. The XLANG/s subservice makes calls to the Message Agent API to insert messages directly. This allows the orchestration engine to insert the message body into the MessageBox and have it directly associated with the running orchestration instance. The persistence of the constructed message in the MessageBox database is coordinated with persistence points in the orchestration as an additional optimization of database operations.

This test helps you determine the number of orchestrations that were created on each host instance, and also tracks the status of these orchestrations over time, thereby promptly alerting you when too many orchestrations are suspended or discarded. The test also tracks the memory usage of the orchestrations, and alerts you if excessive memory is being consumed.

Measurement	Description	Measurement Unit	Interpretation
Idleorchestrations	Indicates the number of idle orchestration instances currently hosted by this host instance.	Number	This refers to orchestrations that are not making progress but are not dehydratable, as when the orchestration is blocked waiting for a receive, listen, or delay in an atomic transaction.
Runningorchestrations	Indicates the number of orchestration instances that are currently executing on this host instance.	Number
Orchestrationscreated	Indicates the number of orchestration instances that are created since this host instance was started.	Number
Orchestcreated	Indicates the rate at which the orchestration instances are created on this host instance.	Orchestrations/sec
Orchestrationscompleted	Indicates the number of orchestration instances that were completed since the host instance was started.	Number
Orchestcompleted	Indicates the rate at which the orchestration instances are completed on this host instance.	Orchestrations/sec	A high value is desired for this measure. A low value or a steady decline in the value of this measure could indicate an execution bottleneck.
Orchestdiscarded	Indicates the number of orchestration instances discarded from memory since this host instance was started.	Number	An orchestration can be discarded if the engine fails to persist in its state.
Orchestdiscardedsec	Indicates the rate at which the orchestration instances are discarded from the memory of this host instance.	Orchestrations/sec
Orchestsuspended	Indicates the number of orchestration instances that are suspended since this host instance was started.	Number	All failures encountered in orchestrations appear as exceptions. If an orchestration does not include any CatchException shape for an exception, the exception causes the orchestration to be Suspended, but not resumable. This means that message and service instance tracking, or a WMI script, cannot recover the instance. However, you can save all messages associated with the Suspended (not Resumable) instance using tracking (or WMI script) for diagnostic and manual retry. To diagnose the problem, use the Orchestration Debugger to see the last shape executed before the instance was suspended. You can also view exception details using the Orchestration Debugger.
Orchestsuspendedsec	Indicates the rate at which the orchestration instances are suspended on this host instance.	Orchestrations/sec
Orchestrehydrated	Indicates the number of orchestration instances that are rehydrated since this host instance was started.	Number	Rehydration is the process of deserializing the last running state of an orchestration from the database. The orchestration engine can be triggered to rehydrate an orchestration instance by the receipt of a message or by the expiration of a time-out specified in a Delay shape. It then loads the saved orchestration instance into memory, restores its state, and runs it from the point where it left off.
Orchestrehydratedsec	Indicates the rate at which the orchestration instances are rehydrated on this host instance.	Orchestrations/sec
Orchestdehydrated	Indicates the number of orchestration instances that are dehydrated since this host instance was started.	Number	Dehydration is the process of serializing the state of an orchestration into a SQL Server database. The orchestration engine might determine that an orchestration instance has been idle for a relatively long period of time. It calculates thresholds to determine how long it will wait for various actions to take place, and if those thresholds are exceeded, it dehydrates the instance. This can occur under the following circumstances: When the orchestration is waiting to receive a message, and the wait is longer than a threshold determined by the engine. When the orchestration is "listening" for a message, as it does when you use a Listen shape, and no branch is triggered before a threshold determined by the engine. The only exception to this is when the Listen shape contains an activation receive. When a delay in the orchestration is longer than a threshold determined by the engine. The engine dehydrates the instance by saving the state, and frees up the memory required by the instance. By dehydrating dormant orchestration instances, the engine makes it possible for a large number of long-running business processes to run concurrently on the same computer. This implies that the larger the number and rate of dehydrations minimal will be the use of system resources.
Orchestdehydratedsec	Indicates the rate at which the orchestration instances are dehydrated on this host instance.	Orchestrations/sec
Pendingmessages	Indicates the number of received messages for which receipt has not yet been acknowledged to the MessageBox from the orchestration.	Number	A very large value could indicate a processing bottleneck.
Pendingworkitems	Indicates the number of execution blocks that are scheduled for execution in the orchestration.	Number
MessageBoxdatabases	Indicates the number of attempted database connections that has failed since this host instance was started.	Number	Ideally, the value of this measure should be 0.
Databasetransactions	Indicates the number of database transactions performed since this host instance was started.	Number
Databasetransactionssec	Indicates the rate of database transactions performed by the orchestrations hosted by this host instance.	Trans/sec
Orchestresidentinmemory	Indicates the number of orchestration instances currently hosted by this host instance.	Number
Mballocatedpvt	Indicates the allocated private memory for this host instance.	MB	This is the current size of memory that this process has allocated that cannot be shared with other processes.
Mballocatedvirtual	Indicates the reserved virtual memory for this host instance.	MB	This is the current size of the virtual address space the process is using. Use of virtual address space does not necessarily imply corresponding use of either disk or main memory pages. Virtual space is finite, and the process can limit its ability to load libraries.
perusedphymem	Indicates the percentage of total physical memory used on this server.	Percent	The dehydration behavior of BizTalk Server depends entirely on how much memory is available and how much memory is being used. The dehydration behavior is different with different amounts of memory and differences in memory use between 32-bit and 64-bit hosts.