Guardian Procedure Calls Reference Manual (G06.25+)

Guardian Procedure Calls (S)
Guardian Procedure Calls Reference Manual—522629-013
14-94
SETMODE Procedure
141,
continued
f -1D positioning is used, the current EOF must be on a page boundary,
otherwise the disk process returns an error. If -1D positioning is used or
writes are done that change the EOF, some performance gains are lost.
When the EOF is changed, DP2 must do extra checkpoints. To avoid the
extra checkpoints, issue a CONTROL 2 to set the EOF to a high value
before starting a series of large writes. When the writes are complete,
another CONTROL 2 can be issued to set EOF to the correct value.
The length of the transfer cannot be more than 57344 bytes. The length
must be a multiple of 2K bytes. Also, some older Expand connections do not
support transfers of more than 30K bytes and return an error if a larger
transfer is attempted.
Large transfer requests are considered repeatable, so no sync ID is passed
to the disk process. If the file is opened with a positive sync depth, normal
retries occur after path failures.
A positive sync depth should not be used with -1D positioning, because
writes to the end of a file are not repeatable. If a path failure occurs,
determine whether the data was written before the path failure. If the data
was not written, issue a retry.
Since DP2's cache is bypassed by these operations and the data is read
from or written to the disk file directly, records or blocks modified by other
openers might not be seen by these requests. The user might see "dirty"
data if access mode and exclusion mode are not set carefully.
142 Select Character Set
param1 = 1 select IBM PC character set.
= 0 select default character set.
param2 is not used with function 142. If supplied, it must be 0.
For 5512, 5515/5516, and 5573 printers, the I/O process sends the following
ESC sequences to select the character set:
ESC(1OU select IBM PC character set.
ESC(1O@ select default character set.
Note:
These printers do not come equipped with the IBM PC character set; it can
be installed later. To use this operation, the printer must have the IBM PC
character set installed on the printer. If the printer does not have the IBM PC
character set installed, the printer ignores the SETMODE 142.
Table 14-4. SETMODE Functions (page 27 of 34)
function Parameters and Effect