ER/Studio - Embarcadero Technologies Product Documentation

USING ER/STUDIO > DEVELOPING THE PHYSICAL MODEL
Table Partition Editor for Oracle 8.x and 9i
• Max Value: (VALUES LESS THAN (MAXVALUE)) Select to create a catch-all partition for values that exceed
all specified ranges. Otherwise, specify a High Value for the partition range.
• High Value: (VALUES LESS THAN (high value)) Specifies the ending value for the partition range.
• Tablespace: Specifies the name of the tablespace on which the table is stored.
• No Logging: Select if you do not want the DLL operations to be logged in the redo file. This can reduce index
creation and updates by up to 30%.
• Pct 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.
• Pct Used: (PCTUSED) Specifies the maximum percentage of available space in each data block before
re-adding it to the list of available blocks. When deletes take place and the room available in a block falls
below this value, the block is made available for new inserts to take place. Tables that won’t be updated should
have this value set to 99. The default value is 40% means that blocks are available for insertion when they are
less than 40% full.
• Initial Trans: (INITTRANS) Specifies the number of DML transactions for which space is initially reserved in
the data block header. Oracle stores control information in the data block to indicate which rows in the block
contain committed and uncommitted changes. The amount of history that is retained is controlled by this
parameter. If too many transactions concurrently modify the same data block in a very short period, Oracle
may not have sufficient history information to determine whether a row has been updated by a “too recent”
transaction. Specify a higher value for indexes that may experience many transactions updating the same
blocks.
• Max Trans: (MAXTRANS) Once the space reserved by INITRANS is depleted, space for additional transaction
entries is allocated out of any available free space. Once allocated, this space effectively becomes a
permanent part of the block header. This parameter limits the number of transaction entries that can
concurrently use data in a data block and therefore limits the amount of free space that can be allocated for
transaction entries in a data block.
• Edit Subpartition button: Launches the Subpartition Editor where you can specify how to subpartition the
partition and where the subpartitions should be stored.
• Initial Extent: (INITEXTENT) Specifies the initial number of data blocks that Oracle should reserve. Oracle
will reserve the number of data blocks that correspond to the initial extent for that table’s rows.
• Next Extent: (NEXT) Specifies the size in kilobytes of the next extent. You should monitor this figure against
the largest available chunk of free space in the tablespace. If a table cannot allocate its next extent, it will no
longer be able to extend and, therefore, cannot accept additional data.
• Pct Increase: (PCTINCREASE) Specifies the percentage by which the next extent should grow over the
previous extent's size. Be careful when setting Percent Increase because it magnifies how an object grows
and, therefore, can materially affect available free space in a tablespace.
• Min Extents: (MINEXTENTS) Specifies the number of extents to allocate when the segment is created.
Controls free space fragmentation by making sure that every used or free extent is at least as large as the
value you specify.
• Max Extents: (MAXEXTENTS) Specifies the maximum number of extents that Oracle can allocate to the index.
Once this limit is reached, Oracle prevents further growth of the cluster and cannot accept additional data.
Carefully monitor the number extents already allocated to the index with this limit.
• Free Lists: (FREELISTS) Specifies the number of free lists to apply to the index. The default and minimum
value is 1. Free lists can help manage the allocation of data blocks when concurrent processes are issued
against the index. Oracle uses the free list to determine which data block to use when an INSERT operation
occurs. Oracle allows table and indexes to be defined with multiple free lists. All tables and index free lists
should be set to the high-water mark of concurrent INSERT or UPDATE activity. For example, if the index has
up to 20 end users performing INSERTs at any time, then the index should have FREELISTS=20.Too low a
value for free lists will cause poor Oracle performance. An increase in FREELISTS or FREELIST_GROUPS can
alleviate segment header contention.
EMBARCADERO TECHNOLOGIES > ER/STUDIO® 8.0.3 USER GUIDE 157