(SYSLIB) Programming Reference Manual - Public Support Login ...

BSP$-Program File Basic Service Package
ο If it is 2, element text length is stated in positions. Position granularity can
be converted to sector granularity by multiplying by 4,096 or by shifting left
by 12 bits.
ο Combinations of element text length and element text length granularity can
result in a number of sectors that are over the theoretical maximum
described above. The result may even be over 36 bits, so maximum value
checks or double-word operations are recommended to determine the
validity of the calculated element text length.
The following are considerations when creating element table entries with the ETIA$
function (see 5.1.7):
• When creating elements in a PF or LPF:
− The maximum element text size is 262,143 sectors.
− The element-text-length granularity (word 3, bits 1 and 2) field should be 0.
− For symbolic elements, element-text-length word 7, bits 6 through 17 (S2 and
S3) should be 0.
− For omnibus elements, element-text-length word 7, bits 12 through 17 (S3)
should be 0.
• When creating elements in an LEPF:
− If the element text is at most 262,143 sectors, use the previous PF and LPF
format for the element table item.
− For efficiency and to avoid wasted mass storage, select the smallest granularity
possible. Sector granularity is the smallest, followed by track and then position.
ο For symbolic elements, the 30-bit element-text-length field is large enough
to describe any element text using sector granularity. Neither track nor
position granularity is needed for symbolic elements.
ο For omnibus elements, the 24-bit element-text-length field is large enough to
describe element text of 16,777,152 sectors using sector granularity. For
element text larger that this, use track granularity. Position granularity is not
needed for omnibus elements.
− When using track or position granularity, make sure that element text length is
rounded up to the next granule, if necessary. For example, 5,000 tracks plus 1
sector (320,001 sectors) must be rounded up to 5,001 tracks (320,064 sectors);
70 positions plus 1 sector (286,721 sectors) must be rounded up to 71 positions
(290,816 sectors).
− If element text length is rounded up, as described above, additional sectors must
be written to pad the element to the proper granule boundary. It is
recommended that sectors containing zeroes be used for the padding. In the
previous examples, the track granularity element would require 63 sectors of
padding and the position granularity element would require 4,095 sectors of
padding.
− When using track or position granularity, make sure that the final element text
length is converted back to number of sectors when updating the FTI next write
location in word FCT+7 (see Figure 5–1).
7833 1733–004 5–37