(B)0[mindex-storage-clause =
[4mSTORE[m qw> index-within-clause qqqqqqqqqqqqqqqqqqqqqqqqqqwqk
m> [4mUSING[m qw> field-name qw> index-within-clause qj x
mqqqqq , <qqqqqj x
lqqqqqqqqqqqqqqqqqqqqqqqq<qqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqj
mqwqqqqqqqqqqqqq>qqqqqqqqqqqqqqwqq>
m> default-threshold-clause qj
The index-storage-clause creates a storage map definition for the
index. It allows you to choose which storage area files will be
used to store index entries. You can store all index entries for
one relation in a single storage area, or you can partition the
entries over multiple storage areas.
1 – index-within-clause
(B)0[mindex-within-clause =
[4mWITHIN[m qwq> area-name qwqqqqqqqqqqqqqq>qqqqqqqqqqqqqqqwqk
x m> [4mWITH[m [4mLIMIT[m OF qw> literal qwj x
x mqqqq , <qqqj x
x lqqqqqqqqqqqqqqqqqqqqqqqq<qqqqqqqqqqqqqqqqqqqqj
x mqwqqqqqqqqqq>qqqqqqqqqqwqqwqqqqqqqqq>
x mq> threshold-clause qj x
mqqqqqqqqqqqqq ; <qqqqqqqqqqqj
1.1 – area-name
The name of the storage area in which you want the index stored.
You must have defined this storage area with either the DEFINE
DATABASE statement or the DEFINE STORAGE AREA clause of the
CHANGE DATABASE statement before you refer to it in the store
clause.
If the index is a hashed index, the storage area must have a
MIXED page format.
1.2 – WITH_LIMIT_OF
The maximum value for the index key that will reside in the
specified storage area.
The number of literals in this clause must be the less than or
equal to the number of fields in the USING clause. Repeat this
clause to partition the index entries among multiple storage
areas.
When you define a multisegmented index using multiple keys and
use the STORE USING...WITH LIMITS clauses, if the values for the
first key are all the same, then set the limit for the first key
at that value. By doing this, you ensure that the value of the
second key determines the storage area in which each record will
be stored.
Note that the last storage area you specify CANNOT have a WITH
LIMIT OF clause associated with it.
1.3 – threshold-clause
(B)0[mthreshold-clause=
qq> [4mTHRESHOLDS[m ARE qqqqqqqqqqk
lqqqqqqqqqqqqq<qqqqqqqqqqqqqj
mq> ( qq> val1 qwqqqqqqqqqqq>qqqqqqqqqqwq> ) qq>
mq> ,val2 qqwqqqqq>qqqqu
mq> ,val3 qj
Specifies associated threshold values for each storage area with
uniform format that is specified in the index-within-clause. By
setting threshold values, you can make sure that Oracle Rdb does not
overlook a page with sufficient space to store compressed data.
The threshold values specify when the page is marked as FULL
in the SPAM page free space inventory lists. For example,
if you set default values of 70, 85, and 95 percent, ranges
of guaranteed free space on each data page are 30, 15, and 5
percent, respectively. If you do not set default values, the
values are (0,0,0). With values of (0,0,0), Oracle Rdb will use the
record length when setting the SPAM fullness. Oracle Rdb will never
store a record on a page at threshold 3. The value you set for
the highest threshold can be used to reserve space on the page
for future record growth.
If you specify a value of 40 for the "val1" parameter, but do not
specify values for the "val2" or "val3" parameters, the threshold
values will be set at (40,100,100).
If you use data compression, you should use logical area
thresholds to obtain optimum storage performance.
2 – field-name
The name of the field that specifies what value will be used as a
limit for partitioning the index across multiple storage areas.
If the index key is multisegmented, you can include some or all
of the fields that are joined to form the index key. Separate
multiple field names with commas.
3 – default-threshold-clause
(B)0[mdefault-threshold-clause =
qq> [4mDEFAULT[m [4mTHRESHOLDS[m ARE qqk
lqqqqqqqqqqqqq<qqqqqqqqqqqqqj
mq> ( qq> val1 qwqqqqqqqqqqq>qqqqqqqqqqwq> ) qq>
mq> ,val2 qqwqqqqq>qqqqu
mq> ,val3 qj
Specifies associated threshold values for each storage area with
uniform format that is NOT specified in the index-within-clause.
By setting threshold values, you can make sure that Oracle Rdb does
not overlook a page with sufficient space to store compressed
data.
The threshold values specify when the page is marked as FULL
in the SPAM page free space inventory lists. For example,
if you set default values of 70, 85, and 95 percent, ranges
of guaranteed free space on each data page are 30, 15, and 5
percent, respectively. If you do not set default values, the
values are (0,0,0). With values of (0,0,0), Oracle Rdb will use the
record length when setting the SPAM fullness. Oracle Rdb will never
store a record on a page at threshold 3. The value you set for
the highest threshold can be used to reserve space on the page
for future record growth.
If you specify a value of 40 for the "val1" parameter, but do not
specify values for the "val2" or "val3" parameters, the threshold
values will be set at (40,100,100).
If you use data compression, you should use logical area
thresholds to obtain optimum storage performance.