X25AM Programming Manual

PTP Applications

X25AM Programming Manual—527201-001

3-2

The PTP File-System Interface

An application accesses the X25AM PTP procedures by using a subset of the

Guardian file-system procedures. This group of file-system procedures is called the

PTP file-system interface.

File-System Procedures Supported by PTP

PTP supports only the file-system procedures that are necessary to perform PTP

tasks. Table 3-1 lists the supported procedures for G-series RVUs. For procedures

added in D-series RVUs, see Appendix C, D-Series Supplement for X25AM.

If you need detailed information about these procedures, refer to the Guardian

Procedure Calls Reference Manual.

Some uses of the PTP file-system interface depend on whether the subdevice is

configured to use a permanent virtual circuit (PVC) or a switched virtual circuit (SVC).

Switched virtual circuits are also referred to as virtual circuits or as virtual calls. The

circuit configuration parameters can be established for all circuits on the line or for

individual circuits configured for subdevices associated with the line.

Initiating a Call

Your application initiates a call when it is necessary to start a data exchange with the

remote device. Initiating a call means that a Call Request is sent and a Call Connected

is received. A PVC does not require call connection. A virtual call requires a successful

call connection for every call.

Before a virtual call is initiated, the address (called address) of the remote device must

be set correctly. The application can set the called address with the SETPARAM 1

procedure. The called address can also be set with the Subsystem Control Facility

(SCF) subdevice attribute DESTADDR.

Your application initiates a virtual call with one of the following file-system procedures:

Table 3-1. Guardian File-System Procedures Supported by PTP for G-Series

RVUs

AWAITIO[X] FILE_GETINFOLIST_ SETMODE

CANCEL FILE_GETINFOLISTBYNAME_ SETMODENOWAIT

CONTROL FILE_GETOPENINFO_ SETPARAM

FILE_CLOSE_ FILE_OPEN_ WRITE[X]

FILE_GETINFO_ READ[X] WRITEREAD[X]

FILE_GETINFOBYNAME_

Note. If your application uses the CANCEL procedure to cancel a READ, data might be lost.

Therefore, do not use CANCEL to terminate outstanding READ requests.