The ARM API

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The ARM API is an Open Group standard for a set of API calls that allow you to measure the performance of any application. The most common use of the API is to measure response time, but it can also be used to record application availability and account for application usage. The ARM API is documented at http://www.opengroup.org/management/arm.htm. The ARM Version 2 implementation is a set of C API calls, as shown in Figure B-2 on page 442.

Figure B-2: ARM API Calls

There are six ARM API calls:

arm_init	This is used to define an application to the response time agent.
arm_getid	This is used to define a transaction to the response time agent. A transaction is always a child of an application.
arm_start	This call is used to start the response time clock for the transaction.
arm_update	This call is optional. It can be used to send a heartbeat to the response time agent, while the transaction is running. You might want to code this call in a long-running transaction, to receive confirmations that it is still running.
arm_stop	This call is used to stop the response time clock when a transaction completes.
arm_end	This call ends collection on the application. It is effectively the opposite of the arm_getid and arm_init calls.

The benefit of using ARM is that you can place the calls that start and stop the response time clock in exactly the parts of the script that you want to measure. This is done by defining individual applications and transactions within the script, and placing the ARM API calls at transaction start and transaction end.

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