ER/Studio - Embarcadero Technologies Product Documentation

USING ER/STUDIO > DEVELOPING THE PHYSICAL MODEL
Sybase Table Storage Options
The options available depend on the database platform.
• DB Space: Specifies the name of the database where the table data is stored.
• Segment: Specifies the name of the segment where the table is stored.
• Locking Scheme: Specifies the locking scheme to implement for DDL transactions.
• ALLPAGES: Locks the data pages and index pages affected by the query.
• DATAPAGES: Locks the data pages but not the index pages, and the lock is held until the end of the
transaction.
• DATAROWS: Locks the individual rows on data pages; rows and pages are not locked. This scheme requires
more overhead but is beneficial for small tables with much contention.
• Max Rows per Page: Specifies the maximum number of rows per page.
• Reserve Page Gap: Specify the reserve gap parameters.
• Identity Gap: Controls the allocation of ID numbers and potential gaps resulting from restarting the server.
Creates ID number blocks of a specific size which improves performance by reducing contention for the table.
Overrides the server-wide identity burning set factor. If the identity gap is set to 1000m the server allocates the
first 1000 numbers and stores the highest number of the block to disk. When all the numbers are used, the server
takes the next 1000 numbers. If after inserting row 2050 the power fails, then when the server restarts it’ll start
with ID 3000, leaving an ID gap of 950 numbers. Each time the server must write the highest number of a block to
disk, performance is affected so you must find the best setting to achieve the optimal performance with the lower
gap value acceptable for your situation.
• Replacement Strategy: Select to use the fetch-and-discard (or MRU) replacement strategy that reads pages
into cache at the most recently-used (MRU) end of the buffer, so it does not flush other pages. But these pages
remain in cache a much shorter time, so subsequent queries are less likely to find the page in cache.
• Prefetch Strategies: Enables or disables large I/O for a session.
Define Table Overflow Options
The Table Editor Overflow tab specifies how to store the overflow records when a row is updated and no longer fits on
the page where it was originally written. The Overflow tab of the Table Editor is available for index-organized tables on
the Oracle 8.x, 9i, 10g and 11g platforms.
1 In the Data Model Window, double-click the table for which you want to specify storage options.
2 From the Table Editor, select the Overflow tab.
3 Complete the Overflow tab options as required and then click OK to exit the editor.
The Overflow tab creates an ORGANIZATION INDEX clause in the CREATE TABLE statement. Any options you
specify on this tab will follow this clause.
The following describes options on the Overflow tab that require additional explanation.
• Tablespace: Specifies the name of the tablespace on which the overflow 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 Threshold: (PCTTHRESHOLD): Specifies the percentage of space reserved in the index block for the
index-organized table. Any portion of a row that exceeds this threshold is stored in the overflow segment.
• Including: (INCLUDING) Select the column to include in the overflow.
EMBARCADERO TECHNOLOGIES > ER/STUDIO® 8.0.3 USER GUIDE 153