HP 3000 Manuals HP 3000 Manuals
Appendix C Database Design Considerations
* Keep one-of-a-kind information, such as unique identifiers, in
master data sets. Keep duplicate information, such as records of
events (sales, purchases, shipments), in detail data sets.
* Define a search item in a detail data set if you want to retrieve
all entries with a common value for that data item.
* Use manual master data sets to prevent entry of invalid data in
the detail search item linked to the master through a path.
Use automatic master data sets to save time if the detail search
items are unpredictable or too numerous to enter manually.
* Limit the use of sort items to paths with relatively short chains
in order to reduce the time required to add and delete entries.
* Select the path most frequently accessed in chained order as the
primary path.
* Remember that data items must be an integral number of halfwords
in length.
* When selecting the maximum block size, consider the environment in
which the database will be used. (Refer to the $CONTROL command
in chapter 3 for more information.)
* If you intend to use QUERY/3000 with your database, refer to the
QUERY/V Reference Manual for the data types that QUERY/3000
supports.
* In application programs either reference data items and data sets
by name or use DBINFO at the beginning of the program to
initialize the data item and data set numbers in order to maintain
data independence of the programs.
* Refer to the discussion in chapter 4 to decide on appropriate
access modes to use for your application programs.
* Analyze the time required to maintain the database, for example,
the time required to unload and load the database. A database
restructuring tool can help keep the time spent on maintenance to
a minimum.
* The capacity of each data set should be defined as realistically
as possible because a capacity that is too large wastes disk
space. The capacity can be increased when necessary by
restructuring the database as described in chapter 8.
* A master data set capacity equal to a prime number or to the
product of two or three primes can yield fewer synonyms than a
master data set capacity of many prime factors. See Figure C-1
for a partial list of prime numbers.
* The account and group in which the database resides must have
enough file space available to contain all the database files.
* If your application uses sorted paths, plan to add or delete
entries (DBPUT, DBDELETE) to sorted chains when the system is not
very busy. If it is very busy, limit the database activity on
sorted chains to reading and updating (DBUPDATE).
* Do all or most of your locking at one level (database, data set,
or data entry).
* If locking at the data entry level, do all or most of the locking
using the same item in each data set. Otherwise, performance will
be the same as if you were locking at the data set level.
* Avoid holding locks around a terminal read.
* Avoid beginning and ending logical transactions around a terminal
read.
* All databases involved in a multiple database transaction must
reside on the same system.
* If transaction logging is used, the database administrator must
ensure that all databases involved in a multiple database
transaction adhere to the following criteria:
* Are enabled for logging.
* Log to the same log file.
* Are either enabled or disabled for roll-back recovery.
* Are either enabled or disabled for MUSTRECOVER.
* For remote database access (applications and databases are not on
the same system), the application's node, the database node, and
all intermediate nodes where a multiple database transaction is
routed must be on TurboIMAGE/XL version C.04.00 or later.
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| |
| 101 280,001 680,003 1,800,017 5,800,019|
| 503 290,011 690,037 1,900,009 5,900,047|
| 1,009 300,007 700,001 2,000,003 6,000,011|
| 5,003 310,019 710,009 2,100,001 6,100,001|
| 10,007 320,009 720,007 2,200,013 6,200,003|
| 15,013 330,017 730,003 2,300,003 6,300,011|
| 20,011 340,007 740,011 2,400,001 6,400,013|
| 25,013 350,003 750,019 2,500,009 6,500,003|
| 30,011 360,007 760,007 2,600,011 6,600,001|
| 35,023 370,003 770,027 2,700,023 6,700,007|
| 40,009 380,041 780,029 2,800,001 6,800,033|
| 45,007 390,001 790,003 2,900,017 6,900,001|
| 50,021 400,009 800,011 3,000,017 7,000,003|
| 55,001 410,009 810,013 3,100,011 7,100,003|
| 60,013 420,001 820,037 3,200,003 7,200,007|
| 65,003 430,007 830,003 3,300,001 7,300,001|
| 70,001 440,009 840,023 3,400,043 7,400,011|
| 75,011 450,001 850,009 3,500,017 7,500,013|
| 80,021 460,013 860,009 3,600,001 7,600,013|
| 85,009 470,021 870,007 3,700,001 7,700,071|
| 90,001 480,013 880,001 3,800,021 7,800,017|
| 95,003 490,001 890,003 3,900,067 7,900,001|
| 100,003 500,009 900,001 4,000,037 8,000,009|
| 110,017 510,007 910,003 4,100,011 8,100,073|
| 121,001 520,019 920,011 4,200,013 8,200,007|
| 130,003 530,017 930,011 4,300,003 8,300,009|
| 140,009 540,041 940,001 4,400,021 |
| 150,001 550,007 950,009 4,500,007 |
| 160,001 560,017 960,017 4,600,003 |
| 170,003 570,001 970,027 4,700,021 |
| 180,001 580,001 980,017 4,800,007 |
| 190,027 590,021 990,001 4,900,001 |
| 200,003 600,011 1,000,003 5,000,011 |
| 210,011 610,031 1,100,009 5,100,071 |
| 220,009 620,003 1,200,007 5,200,007 |
| 230,003 630,017 1,300,021 5,300,003 |
| 240,007 640,007 1,400,017 5,400,001 |
| 250,007 650,011 1,500,007 5,500,003 |
| 260,003 660,001 1,600,033 5,600,027 |
| 270,001 670,001 1,700,021 5,700,007 |
| |
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Figure C-1. Selected Prime Numbers