An Applicazione Arbortext PE does not need to be thread-safe. An Sottoprocesso Arbortext PE only handles one request at a time; therefore, it can only run one Applicazione Arbortext PE at a time. However, an Applicazione Arbortext PE does need to be safe for multi-processing, because the Arbortext PE Request Manager could ask two or more Sottoprocessi Arbortext PE to run the same Applicazione Arbortext PE at the same time.

For example, if an Applicazione Arbortext PE attempts to write temporary data using an absolute path and file name (e:\tempdata\tempdatafile.txt), two instances of the Applicazione Arbortext PE might run at the same time and overwrite each other’s file. If an Applicazione Arbortext PE stores data to the Windows clipboard, two instances of the operation might run simultaneously and interfere with each other.

Every Applicazione Arbortext PE needs to be serially reusable. An Applicazione Arbortext PE should not attempt to maintain any state from one call to the next. The Arbortext PE Request Manager could ask a particular Sottoprocesso Arbortext PE to execute any Applicazione Arbortext PE repeatedly, so the Applicazione Arbortext PE must not assume any prior state each time it is invoked. If a particular client submits several Applicazione Arbortext PE requests to an Server Arbortext PE, the Arbortext PE Request Manager might allocate a different Sottoprocesso Arbortext PE to serve each request. If the second request expects to find information left behind by the first request (for example, a value stored in a global variable), the application would only work if the Arbortext PE Request Manager happened to allocate the same Sottoprocesso Arbortext PE to serve both requests.