(B)0[mstorage-area-options = qwwqqqqqqqqqqqqqqqqqqqqqqqqqqq>qqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqwwq> xtqq> [4mALLOCATION[m IS qqq> number-pages qqqq>qqqqqqqqq PAGES qqqqux xtqq> [4mPAGE[m [4mSIZE[m IS qqqq> page-blocks qqqqq>qqqqqqqqq BLOCKS qqqux xtqq> [4mPAGE[m [4mFORMAT[m IS qqwqqqq> [4mUNIFORM[m qqqqwqqqqqqqqqqqqqqqqqqqqux xx mqqqq> [4mMIXED[m qqqqqqj xx xtqq> [4mTHRESHOLDS[m ARE q> ( q> val1 wqqqqqqqqqqqqqqqqqqqqwq> ) qqux xx m> ,val2 wqqqqqqqqqwqj xx xx m> ,val3 qj xx xtqq> [4mINTERVAL[m IS qqqqqqq> number-data-pages qqqqqqqqqqqqqqqqqqux xtqq> [4mSNAPSHOT_FILENAME[m [4mIS[m qqqq> file-spec qqqqqqqqqqqqqqqqqqqqux xtqq> [4mSNAPSHOT[m [4mALLOCATION[m IS qqq> snp-pages qqq> PAGES qqqqqqqqux xtwq> [4mSNAPSHOT[m [4mEXTENT[m IS qwqqwq> extent-pages qqqq> PAGES qwqqqux xxmq> [4mEXTENT[m IS qqqqqqqqqqj mq> extension-options qqqqqqqqj xx xmqq> [4mWRITE_ONCE[m qqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqjx mqqqqqqqqqqqqqqqqqqqqqqqqqqqq<qqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqj
1 – number-pages
The number of database pages allocated to the database initially.
Oracle Rdb automatically extends the allocation to handle the
loading of data and subsequent expansion. The default is 400
pages.
2 – page-blocks
The size in blocks of each database page. Page size is allocated
in 512-byte blocks. The default is two blocks (1024 bytes). If
your largest record is larger than approximately 950 bytes,
allocate more blocks per page to prevent records from being
fragmented.
3 – PAGE_FORMAT
Specifies whether a storage area contains uniform or mixed pages.
You can use the PAGE FORMAT option with multifile databases
only. In storage areas with uniform page format, all pages in
a specific logical area contain records from the same relation.
In storage areas with mixed page format, pages can hold records
from different relations. The default is UNIFORM.
4 – THRESHOLDS
Specifies one, two, or three threshold values. The threshold
values represent a fullness percentage on a data page and
establish four possible ranges of guaranteed free space on the
data pages. When a data page reaches the percentage defined by
a given threshold value, the SPAM entry for the data page is
updated to reflect the new fullness percentage and its remaining
free space.
The default thresholds are 70, 85, and 95 percent. When
THRESHOLDS ARE is used, the first threshold value is required.
If you specify only one or two values, unspecified values default
to 100 percent. You can specify the THRESHOLDS option only on a
storage area for a multifile database. Threshold values can be
set for storage areas with MIXED or UNIFORM storage area page
formats.
5 – number-data-pages
Specifies the number of data pages between SPAM pages in the
physical storage area file, and thus the maximum of data pages
each SPAM page will manage. The default, and also the minimum
interval, is 256 data pages. The first page of each storage
area is a SPAM page. The interval you specify determines where
subsequent SPAM pages are to be inserted, provided there are
enough data pages in the storage file to require more SPAM pages.
You can specify the INTERVAL option only on a storage area for a
multifile database. The storage area page format must be MIXED.
6 – file-spec
Provides a separate file specification for the snapshot file.
Do not specify a file extension other than SNP to the file
specification. You cannot specify a global default for the
SNAPSHOT_FILENAME. Thus, in a multifile database, the SNAPSHOT_
FILENAME option must be within a DEFINE STORAGE AREA definition.
The SNAPSHOT_FILENAME option cannot be specified for a single-
file database.
7 – snp-pages
Specifies the number of pages allocated for the snapshot file.
The default is 100 pages.
8 – extent-pages
Specifies the number of pages of each extent. The default is 100
pages.
9 – extension-options
Specifies the MIN, MAX, and percent growth of each database file
extent. Enclose the parameter list in parentheses.
(B)0[mextension-options =
qqq> ( qqq> [4mMINIMUM[m OF qq> min-pages qqq> PAGES, qk
lqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqj
mqq> [4mMAXIMUM[m OF qq> max-pages qq> PAGES,qk
lqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqj
mqq> [4mPERCENT[m [4mGROWTH[m IS qqq> growth qqqq> ) qqq>
9.1 – min-pages
Specifies the minimum number of pages of each extent. The default
is 99 pages.
9.2 – max-pages
Specifies the maximum number of pages of each extent. The default
is 9,999 pages.
9.3 – growth
Specifies the percent growth of each extent. The default is 20
percent growth.
10 – WRITE_ONCE
You can use the WRITE_ONCE option to change a storage area
containing stable segmented string data to a format that can
be stored on a write-once, read-many (WORM) optical disk. A WORM
optical disk offers a relatively inexpensive way of storing large
amounts of data for read-only access compared to other storage
media.
The following restrictions apply to the WRITE_ONCE option:
o Note that you cannot write data other than segmented strings
to a write-once storage area. Oracle Rdb issues an error message
if you try to create a storage map that stores data other than
segmented strings in a write-once storage area. Storage maps
for non-segmented-string data must be removed before you can
alter a storage area to WRITE_ONCE.
o When you create a storage area on WORM media, you must specify
that the snapshot area remains on read/write media: do not
give a snapshot file the WRITE_ONCE attribute.
o If you specify the WRITE_ONCE option when storing a segmented
string, database keys are not compressed. For more information
on database key compression, see the Oracle Rdb Guide to Database
Maintenance.
o Write-once storage areas do not use SPAM pages to look for
storage space, but to assist moving data back to non-WORM
media in which SPAM pages must be built again, space is still
allocated for them. Since SPAM pages are essential in uniform
areas, Write-once storage areas cannot be of uniform format
and therefore are required to be of mixed format.
o You can use the PAGE SIZE IS clause of CREATE STORAGE AREA to
change the default page size for a storage area. You should
specify an even number of blocks per page. The smallest amount
of space used in a write operation to WORM media is 1024 bytes
(2 blocks). Therefore, by specifying an even number of blocks
per page, you minimize the space wasted when writing segmented
strings to WORM media.
o Rdb does not support magnetic media for storing write-once
storage areas.
o After you move a storage area to or from a WORM device,
Do a full and complete backup of your database with the
RMU/BACKUP command and start a new after-image journaling
file. For more information on backup and recovery procedures
with write-once storage areas, see the Oracle Rdb Guide to
Database Maintenance.