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Guardian Programming Reference Summary for C

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SETMODE Operations
Guardian Programming Reference Summary for C—522630-001
11-23
141,
continued
The length of the transfer cannot be more than 57,344 bytes. The length must be
a multiple of 2K bytes. Although up to 56K bytes are transferred to the disk
process in one operation, the actual transfer to the disk might not be 56K bytes at
once. The disk process must do the actual data transfer to the disk in smaller
pieces if more than one file extent is crossed or the controller is not a 3107 or
3108. Also, some 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.
The param2 parameter is not used with function 141. 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(1OUselect 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.