Subsystem Control Point (SCP) Management Programming Manual

SPI Programming Considerations for SCP
Subsystem Control Point (SCP) Management Programming Manual—520619-001
3-8
Obsolete Fields in Structured Tokens
However, if the SCP process cannot fit a value in an obsolete token, it omits the token
from the response and stores the value in a new token. The subsystem does not return an
error. The requester does not discover the problem until it encounters the error ZSPI-
ERR-MISTKN when it tries to get the old token from the buffer.
Obsolete Fields in Structured Tokens
Similar considerations apply to the fields of structured tokens. If new data fits in an
obsolete field, the SCP process returns the obsolete field in the structured token.
If the new data does not fit in the old field, and no null value is defined, the entire
structured token is omitted from the response. A new structured token with expanded
fields is returned in its place.
If the data does not fit in the obsolete field, and the field has a defined null value, the
null value is returned. If the token is an extensible structured token, the value might be
returned in a new field appended to the structure; otherwise, the value is returned in a
new simple token.
SCP processes encounter this situation, for instance, in the cases of the information
structures returned in INFO, LISTDEV, and STATUS responses:
ZSCP-MAP-INFO-PROC
ZSCP-MAP-LISTDEV-PROC
ZSCP-MAP-STATUS-PROC
The LISTDEV and STATUS structures contain fields used to convey process IDs. Each
process ID consists of a CPU number and a process identification number (PIN), both of
which are stored in a single integer field (8 bits allocated to each). Because 8 bits is not
adequate to represent the possible range of PIN values in a D-series environment, new
structures are defined with larger fields:
ZSCP-MAP-XLISTDEV-PROC
ZSCP-MAP-XSTATUS-PROC
Where an obsolete structure represents a PID in a single integer, the corresponding new
structure uses two integer fields: one for CPU and one for PIN. When the PIN value fits
in 8 bits, SCP stores it in both the obsolete structure and current structure. However, if
the value does not fit, as when describing a high-PIN process, the SCP process omits the
obsolete structure from the response (because this field has no defined null value). No
error or warning is issued.
All three preceding obsolete structures contain fields that convey file names. These
fields are limited to 32 characters, a limit which can be exceeded in D-series and G-
series environments. If the file name does not exceed 32 characters, it is returned in both
the obsolete structure and a corresponding current token. If the name is too long for the
obsolete structure, that structure is omitted from the response.
Caution. SCP processes do not return an error to indicate that an obsolete field of a
structured token was set to its null value because it would not accomodate new data.