SNAX/HLS Application Programming Manual

2 Connection Types
104707 Tandem Computers Incorporated 2–1
Communication between a user application program and SNAX/HLS is through the
standard interprocess communication protocol. The application program establishes
the connection using an OPEN request to the Tandem NonStop Kernel, specifying as a
file-name the name of the SNAX/HLS server or the LU name. The Tandem
NonStop Kernel returns a logical file number, which is used in all I/O requests dealing
with the connection opened. Depending on the information specified in the file name,
the connection resulting from the OPEN operation can be a specific connection or a
server connection. Both of these connection types are discussed in this section.
Specific Connection A specific connection allows access to only the LU designated in the OPEN statement.
This connection is the result of opening the SNAX/HLS server with a file-name
defined as follows:
$HLS-process–name.qualifiers
where qualifiers name a specific LU and the actual entities they refer to depend on
the Tandem SNA access method being used.
If the access method is SNAX/XF, then qualifiers are:
#SNAX/XF–linename.LU–name
If the access method is SNAX/CDF, then qualifiers are:
#CDF–process–name.openname–of–SNAX/CDF–appl
For example
$HLS.#SNA1.LU1
refers to the process named $HLS, the SNAX/XF line named $SNA1, and the LU
named #LU1.
Once a specific connection is made, any OPEN-SESSION or HLS-ALLOCATE verbs
issued over that connection must either specify a blank LU-name or the exact name
used on the OPEN statement.
When the connection is severed, either explicitly by a CLOSE or implicitly by process
termination, any session resources allocated for the LU are automatically closed and
deallocated.
Server Connection The distinguishing feature of server connections is that SNAX/HLS allows multiple
server connections from a single process and all such connections are equivalent. For
example, an OPEN-SESSION issued on one such link makes that session accessible
through all server links from the same process. This connection is the result of
including in the file name the name of the SNAX/HLS server and no qualifiers.
When the last link from a process is closed (or the process terminates), SNAX/HLS
automatically closes and deallocates all relevant resources.