Estimate Size

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The Estimate Size dialog for tables and indexes lets you estimate how large a table or index will become given a row growth projection. The results let you proactively plan your space-related object needs.

Platform Availability

• ORCL, SYB ASE

To Estimate Size for a Table or Index

1. Initiate an Estimate Size action against one or more tables or indexes. For more information see Initiating an object operation.

   The Estimate Size dialog opens.

2. Use the following topics as a guide to estimating size and using the other options offered on this dialog:
   • Estimating Oracle index or table sizes
   • Estimating Sybase ASE index or table sizes

Estimating Oracle index or table sizes

The Estimate Size dialog remains open until you manually close it. This lets you run several estimations, varying the method and various metrics. Each estimation run is a three-step process:

1. Select a size estimation method:
   • Use current row data from current statistics - The table or index must have been previously analyzed for statistics to be obtained. Note that the Analyze Index(es) and Analyze Table(s) buttons can be used to initiate this action. For more details, see Analyze.
   • Use table/index definition source - The maximum row length for the index or table will be calculated. Note that this usually produces much higher space estimates.
   • Manually enter estimation metrics - Manually enter in data for space estimates if the objects have no data or if the index definition source method is not desired.
2. Depending on the method you chose, provide additional metrics:
   • Percent Free
   • Row Size
   • Number of rows
3. Click the Estimate Size button and view the estimate in the Estimated Index Size box.

Other options include:

• Use the Report button to generate an HTML report of results
• Use the Save As button to save a result grid file
• Use the Owner and Name controls to select another table or index for size estimates.
• Use the Add Index or Add Table button to add another table or index to your size estimates. Similarly, use the Remove Index or Remove Table button to remove a table or index from the dialog.

Estimating Sybase ASE index or table sizes

The Estimate Size dialog remains open until you manually close it. This lets you run several estimations, varying the available metrics. Each estimation run is a two-step process:

1. Provide the metrics for your estimate:
   • Fill Factor (indexes only) - Specify a percentage of how full each index page can become.
   • Number of rows - Specify the number of rows for your size estimate.

   Note: Optionally you can use the Update Statistics button to open a dialog that lets you generate new statistics for the index or table. For details, see Update Statistics.

2. Click the Estimate Size button and view the estimate in the Estimated Index Size box.

Other options include:

• Use the Report button to generate an HTML report of results
• Use the Save As button to save a result grid file
• Use the Database, Owner, Table Name, and Index Name controls to select another table or index for size estimates.
• Use the Add Index or Add Table button to add another table or index to your size estimates. Similarly, use the Remove Index or Remove Table button to remove a table or index from the dialog.