1  CHANGE_STORAGE_MAP
   Changes the storage map definition for a relation. You can also
   change which index Oracle Rdb uses when it stores new records
   whether records will be stored in a compressed format, and
   whether data will be reorganized.
 

2  Format

 (B)0CHANGE STORAGE MAP map-name qq>qqk
 lqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqj
 mwqqqqqqqqqqq>qqqqqqqqqqwqwqqqqqqqqqqqqqqq>qqqqqqqqqqqqqqwk
  m> map-storage-clause qj m> change-relation-map-clause qjx
 lqqqqqqqqqqqqqqqqqqqqqqqqqqq<qqqqqqqqqqqqqqqqqqqqqqqqqqqqqj
 mq> END qqqqqwqqqqqqqq>qqqqqqwqqqqq> STORAGE MAP qqqq> .
              mq> map-name qqqj

 

3  map-name
   The name of the storage map you want to modify.
 

3  map-storage-clause

 (B)0map-storage-clause =
 
 STORE qw> map-within-clause qqqqqqqqqqqqqqqqqqqqqqqqqqwqk
        m> USING qw> field-name qw> map-within-clause qj x
                  mqqqqq , <qqqqqj                       x
  lqqqqqqqqqqqqqqqqqqqqqqqq<qqqqqqqqqqqqqqqqqqqqqqqqqqqqqj
  mqwqqqqqqqqqqqqq>qqqqqqqqqqqqqqwqq>
    m> default-threshold-clause qj

   Used to define a storage map. This clause lets you specify which
   storage area files will be used to store rows from the relation:

   o  All rows of a relation can be associated with a single storage
      area.

   o  Rows of a relation can be randomly distributed among several
      storage areas.

   o  Rows of a relation can be systematically distributed, or
      partitioned, among several storage areas by specifying upper
      limits on the values for a column in a particular storage
      area. This is called horizontal partitioning.

   If you omit the storage map definition, the default is to store
   all the rows for a relation in the main RDB$SYSTEM storage area.
 

4  map-within-clause

 (B)0map-within-clause =
 
 WITHIN qwq> area-name qwqqqqqqqqqqqqqq>qqqqqqqqqqqqqqqwqk
         x              m> WITH LIMIT OF qw> literal qwj x
         x                                mqqqq , <qqqj  x
         xlqqqqqqqqqqqqqqqqqqqqqqq<qqqqqqqqqqqqqqqqqqqqqqj
         xmwqqqqqqqqqqqqqqqqqqqqqq>qqqqqqqqqqqqqqqqqqwqwqk
         x mq> FOR qwqwqw> rel-name qwqqqqqqqqqqqqqqqu x x
         x          x x mqqqq , <qqqqj               x x x
         x          x mw> relation-name.field-name qwj x x
         x          x  mqqqqqqqqqqqq , <qqqqqqqqqqqqj  x x
         x          mqqqqqqqqqqqq , <qqqqqqqqqqqqqqqqqqj x
         x lqqqqqqqqqqqqqqqqqqqqqqqq<qqqqqqqqqqqqqqqqqqqqj
         x mqwqqqqqqqqqq>qqqqqqqqqqwqqwqqqqqqqqq>
         x   mq> threshold-clause qj  x
         mqqqqqqqqqqqqq ; <qqqqqqqqqqqj

 

5  area-name
   The name of the storage area you want records stored in. 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.
 

5  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.

   If you change the limits for a storage area, records that were
   already stored in the area are not moved according to the new
   limit clause. However, new records will be stored into the
   relation according to the new limits you specify.
 

5  rel-name
   The name of the relation whose segmented strings you want to
   store in the specified storage area. If you want to store the
   segmented strings of more than one relation in the storage area,
   separate the names of the relations with commas.
 

5  relation-name.field-name
   The name of the relation and segmented string field that you want
   to store in the specified storage area. If you want to store more
   than one segmented string field in the storage area, separate the
   list items with commas.
 

5  threshold-clause

 (B)0threshold-clause=
 
 qq> THRESHOLDS 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 map-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.
 

4  USING_field-name
   The names of the fields whose values will be used as limits for
   partitioning the relation across multiple storage areas. Oracle Rdb
   compares values in the fields to the values in the WITH LIMIT OF
   clause to determine where to initially store the record.
 

4  default-threshold-clause

 (B)0default-threshold-clause =
 
 qq> DEFAULT THRESHOLDS 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 map-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.
 

3  change-relation-map-clause

 (B)0change-relation-map-clause =
 
 qqwwq> NO PLACEMENT VIA INDEX qqqqqqqqqqqqqqqwq>
   xmq> PLACEMENT VIA INDEX  qq> index-name qqu
   twq> DISABLE qqwq> COMPRESSION qqqqqqqqqqqqu
   xmq> ENABLE qqqj                           x
   mqq> REORGANIZE qqqqqwqqqqqq>qqqqwqqqqqqqqqj
                        tq> AREAS qqu
                        mq> PAGES qqj

 

4  PLACEMENT_VIA_INDEX
   Indicates that Oracle Rdb should attempt to store a record in a
   way that optimizes access to that record via the indicated path.
   Oracle Rdb chooses a target page for any record being stored by
   rules that take into account the type of index defined (sorted or
   hashed), the type of storage areas involved (uniform or mixed),
   and how indexes and relations are assigned to each other.

   The index named in the PLACEMENT VIA INDEX clause must be defined
   for the same relation that the storage map is being defined for.
 

4  NO_PLACEMENT_VIA_INDEX
   Negates the PLACEMENT VIA INDEX clause, so that subsequent
   records stored are not stored via the index named in the
   PLACEMENT VIA INDEX clause. This option is only available on the
   CHANGE STORAGE MAP statement. If you specify the CHANGE STORAGE
   MAP statement without the PLACEMENT VIA INDEX option or the NO
   PLACEMENT VIA INDEX option, the statement executes as if the
   clause specified on the DEFINE STORAGE MAP statement or last
   CHANGE STORAGE MAP statement had been used.
 

4  COMPRESSION_clause
   Specifies whether data compression will be enabled or disabled
   for the records when they are stored. ENABLE COMPRESSION is the
   default.
 

4  REORGANIZE_clause
   Causes rows previously stored in specified relations to be moved
   according to the partitions specified in the CHANGE STORAGE MAP
   statement.
 

2  More
   To change a storage map for a relation with the CHANGE STORAGE
   MAP statement, you need the Oracle Rdb CHANGE privilege for the
   relation.

   If the database is created with the DICTIONARY IS REQUIRED
   option, you must invoke the database by path name, rather than
   file name, before you issue this statement.

   You must specify either a store-clause, a [NO]PLACEMENT VIA INDEX
   clause, a REORGANIZE clause, or a COMPRESSION clause in a CHANGE
   STORAGE MAP statement.

   In the change-relation-map-clause, you can select one or more of
   the three clauses ([NO]PLACEMENT VIA INDEX clause, REORGANIZE
   clause, or COMPRESSION clause) in any order, but you cannot
   repeat a clause. Note that when the REORGANIZE clause is used,
   records are moved and assigned to new dbkeys.

   If you omit the store-clause in the CHANGE STORAGE MAP statement,
   you can create a second index by mistake.

   You must execute this statement in a read/write transaction.
   If there is no active transaction and you issue this statement,
   Oracle Rdb starts a read/write transaction implicitly.

   Other users are allowed to be attached to the database when you
   issue the CHANGE STORAGE MAP statement. However, they are not
   allowed to be using the relation whose map is being changed.
 

2  Examples
   Example 1

   The following example disables compression for the CANDIDATES_MAP
   storage map:

   RDO>  CHANGE STORAGE MAP CANDIDATES_MAP
   cont>   DISABLE COMPRESSION
   cont> END CANDIDATES_MAP STORAGE MAP.

   Example 2

   The following example assigns new limits for storage areas:

   RDO>  CHANGE STORAGE MAP EMPLOYEES_MAP
   cont>  STORE USING EMPLOYEE_ID
   cont>    WITHIN EMPIDS_LOW WITH LIMIT OF "00300";
   cont>           EMPIDS_MID WITH LIMIT OF "00600";
   cont>           EMPIDS_OVER
   cont> END EMPLOYEES_MAP STORAGE MAP.

   Current data will not be moved according to the new limits.
   However, when new data is stored, it will be stored according
   to the new limits in the storage map.

   Example 3

   The following example defines a new storage area EMPIDS_MID2 to
   handle the employee IDs 600-900, and to reorganize the data from
   one existing storage area, EMPIDS_OVER. The current data which
   is stored within the limits of employee IDs 601-900 will be moved
   according to the new limits. When the new data is stored, it
   will be stored according to the new limits set in the storage map
   definition.

   RDO> CHANGE STORAGE MAP EMPLOYEES_MAP
   cont>  STORE USING EMPLOYEE_ID
   cont>        WITHIN EMPIDS_LOW WITH LIMIT of "00300";
   cont>           EMPIDS_MID WITH LIMIT OF "00600";
   cont>           EMPIDS_MID2 WITH LIMIT OF "00900";
   cont>           EMPIDS_OVER
   cont>           REORGANIZE
   cont> END EMPLOYEES_MAP STORAGE MAP.