ER/Studio - Embarcadero Technologies Product Documentation

USING ER/STUDIO > DEVELOPING THE PHYSICAL MODEL
• Partitioned: Select if you want to partition the index. Then the options in the Index Partitions Editor accessible
from the Partitions tab become available. For more information, see Partitioning a Table Index.
• Using Claus: (USING) Specifies what kind of index space is created for the index and who manages the index. If
you do not specify a USING claus, DB2 manages the index space on volumes listed in the default storage group
of the table’s database, which must exist. DB2 uses the defaults values PRIQTY, SECQTY, and Erase Data.
• VCAT: (VCAT) If selected, allocates space for the index on a data set managed using the virtual catalog (VCAT)
whose name is specified next to this option, and the user manages the data sets required for the index. The
VCAT method is usually used for defining system catalogs. It requires that the VSAM dataset be pre-defined
before the index space is created.
• STOGROUP: (STOGROUP) If selected, stores the index on a data set managed by DB2 in the named storage
group. Stogroup defined index spaces let DB2 do all the VSAM allocation work for you. If you have created a
Stogroup for the data model, using the Stogroup Editor (see Creating and Editing StoGroups), you can select that
Stogroup from the list. If you select Stogroup, you can also define values for PRIQTY and SECQTY. To prevent
wasted space for non-partitioned indexes, you should not define PRIQTY and SECQTY; instead let DB2 manage
the amount of primary and secondary space allocated for the index.
• PRIQTY:(PRIQTY) Specifies the minimum number of disk space in kilobytes to initially allocate for the index.
The primary allocation should be large enough to handle the storage needs that you anticipate.
• SECQTY: (SECQTY) Specifies the amount of disk space in kilobytes to allocate to the index when it reaches
the size of the primary allocation. If the secondary allocation space is too small, the data set might have to be
extended more times to satisfy those activities that need a large space. The default value of -1 indicates that
DB2 should determine the size of the secondary allocation, which is usually 10% of the primary allocation.
• Erase Data: (ERASE) If selected, specifies to erase the index data set when the index is deleted.
• None: If selected, no USING claus is included in the CREATE INDEX statement.
• Buffer Pool: (BUFFERPOOL) Identifies the buffer pool to be used for the index. The buffer pool used determines
how the data blocks are cached in memory, in order to facilitate faster data access. BP0 is the default buffer pool
for sorting.
• Percent Free: (PCTFREE) Specifies the maximum percentage of space in each data block to reserve for future
updates. This reserved space helps to avoid row migration and chaining caused by an update operation that
extends a data row's length. Tables that won’t be updated should have this value set to 0.
• Free Page: (FREEPAGE) Specifies how often to leave a page of free space when index entries are created. One
free page is left for every number of pages specified here in the range of 0 to 255.
• Piece Size: (PIECESIZE) Specifies the maximum addressable space of each data set for a secondary index.
Specify the size followed by K (kilobyte), M (Megabyte), of G (Gigabyte). If you do not specify the unit of measure,
kilobytes is assumed. Sizes specified in gigabytes are converted to megabytes in the DDL.
• GBP Cache: (GPBCACHE) In a data sharing environment, specifies what index pages are written to the group
buffer pool. This option is ignored in a non-data-sharing environment unless the index is on a declared temporary
table. Specify Changed to write updated pages to the group buffer pool, All to cache all pages to the group buffer
pool as they are read in from DASD or None to indicate that the buffer pool is only to be used for
cross-invalidation.
Informix Index Options
• Unique: (UNIQUE) If selected, specifies that the index key contains no duplicate values and therefore every row
in the table is in some way unique. If not selected, a non-unique index is created that lets table rows have
duplicate values in the columns that define the index.
EMBARCADERO TECHNOLOGIES > ER/STUDIO® 8.0.3 USER GUIDE 171