ER/Studio - Embarcadero Technologies Product Documentation

USING ER/STUDIO > DEVELOPING THE PHYSICAL MODEL
• Max Trans: (MAXTRANS) Specifies the maximum number of concurrent transactions that can update a data block
to avoid performance problems. 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.
• 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. 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: (MINEXTENT) 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: (MAXEXTENT) Species the maximum number of extents that Oracle can allocate to the materialized
view. 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 table with this limit.
• Free Lists: (FREELISTS) Specifies the number of free lists to apply to the table. 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 table 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.
• Free List Groups: (FREELIST GROUPS) Applicable only if you are using Oracle with the Parallel Server option in
parallel mode. Specifies the number of free list groups which allow the table to have several segment headers.
This enables multiple tasks to insert into the index; thereby alleviating segment header contention. Free list
groups should be set to the number of Oracle Parallel Server instances that access the index. For partitioned
objects and cases of segment header contention, free list groups my be set for non-RAC systems.
• Buffer Pool: (BUFFER_POOL) Specifies the memory structure that is used for caching data blocks in memory,
providing faster data access.
• DEFAULT caches data blocks in the default buffer pool.
• KEEP retains the object in memory to avoid I/O conflicts.
• RECYCLE removes data blocks from memory as soon as they are no longer in use, thereby saving cache
space.
EMBARCADERO TECHNOLOGIES > ER/STUDIO® 8.0.3 USER GUIDE 151