Seek - Control Data Corporation 3300 Reference Manual

4.7.22
SEEK
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The SEEK statement initiates access to a mass storage data record for sub-
sequent reading or writing.
SEEK file-name RE CORD
A SEEK statement pertains only to mass storage files in the random access
mode and, when specified, is executed before each READ and WRITE statement.
SEEK finds the location of the record to be accessed from the contents of the
ACTUAL KEY identifier. The user is responsible for setting the contents of
this identifier prior to execution of the SEEK statement (see ACTUAL KEY,
section 2.3.1). Validity of the contents of the ACTUAL KEY identifier for the
particular mass storage file is determined at the time of execution. If the
key is invalid, the imperative statement in the INVALID KEY clause of the
next READ or 'WRITE statement for the associated file is executed.
Two SEEK statements for the same mass storage file may logically follow each
other. Any validity check associated with the first SEEK statement is negated
by execution of a second SEEK statement.
CAUTION: The intent of the SEEK statement is to provide an overlap
of actual processing while the read/write heads on a mass storage
device are being positioned to the next data block that will be refer-
enced by a subsequent READ or WRITE request. The advantage
gained in the SEEK statement may be lost if other programs within
the MASTER multiprogramming environment are accessing the
same mass storage device. Therefore, the SEEK statement should
be used only on random files that do not share mass storage devices
with other files.
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