HP 3000 Manuals HP 3000 Manuals
$CONTROL
The $CONTROL command allows you to specify options in relation to
processing the schema.
Syntax
$CONTROL [LIST ] [,ERRORS=nnn] [,LINES=nnnnn] [,ROOT ]
[NOLIST] [,NOROOT]
[,BLOCKMAX=nnnn] [,TABLE ]
[,NOTABLE]
Parameters
LIST causes each source record of the schema to be printed on
the list file.
NOLIST specifies that only source records with errors be
printed on the list file. An error message is printed
after these records.
ERRORS=nnn sets the maximum number of errors to nnn. If more than
nnn errors are detected, the Schema Processor
terminates. nnn can have a value between 0 and 999,
inclusive. The default value is 100.
LINES=nnnnn sets the number of lines per page on the list file to
nnnnn which can be between 4 and 32767, inclusive. The
default value is 60 if the list file is a line printer
and 32767 if it is not.
ROOT causes the Schema Processor to create a root file if no
errors are detected in the schema. This is the default.
NOROOT prevents the Schema Processor from creating a root file.
BLOCKMAX=nnnn sets the maximum physical block length (in halfwords)
for any data set in the database. nnnn can have a value
between 128 and 2560, inclusive. The default value is
512. This is an important parameter and is discussed in
detail in the section "Selecting the Block Size."
TABLE causes the Schema Processor to write a table of summary
information about the data sets to the list file device
if no errors are detected. This is the default.
NOTABLE suppresses the TABLE option.
Description
The default parameters are LIST, ROOT, and TABLE. If no $CONTROL command
is used, the results are the same as if the following $CONTROL command is
used:
$CONTROL LIST,ERRORS=100,LINES=60,ROOT,BLOCKMAX=512,TABLE
The parameters can be placed in any order but must be separated by
commas.
Selecting the Block Size
The data set records are transferred from the disk to memory in 4096-byte
pages in TurboIMAGE/XL blocks. The block format is described in chapter
10. When you specify a maximum block size with the $CONTROL command, you
should consider:
* Efficient disk space utilization.
* Localizing the block's bit map to the actual data entries within a
4096-byte page.
The Schema Processor determines the number of data records that fit in a
block. Note that DBSCHEMA chooses a block size (less than or equal to
the maximum block size) that makes the best use of disk space, and which
can be substantially less than the maximum block size specified by
$CONTROL BLOCKMAX (or the default of 512 halfwords). If the record size
is greater than 512 halfwords, BLOCKMAX must be set greater than or equal
to the record size. A certain amount of tuning may be necessary to
determine the best block size. In general, the default block size of 512
halfwords yields reasonable performance on TurboIMAGE/XL and should be
changed only when needed.