How much free hard disk space is required?

Category: Troubleshooting & error messages
Date: 16 Jul 2009
Product: SQL Data Compare
I encounter messages stating that I am out of disk space when using SQL Data Compare on my larger databases. What are the disk space requirements for comparing large databases?

As a rule of thumb you need 3-4 times the size of the database free disk space (This is for a local copy of the data from each database and space for the SQL Script creation). If your databases contain very similar data in both instances then we would suggest looking at the option "Show identical values in results" under "Comparison Options" on the options tab as this will stop data compare storing any data which is identical in the two databases allowing the comparison to happen with a much smaller disk space footprint.

If your databases contain a large amount of different data then I would suggest splitting the table horizontally or vertically and performing the comparisons in parts. You can split the table horizontally by using the "WHERE filter" feature. On the "Tables and Views" tab right click on the tables with a large amount of data in them and choose "Open WHERE clause editor" this will open up a window where you can specify a where clause and split the table into parts.

You can also do the equivalent vertically by clicking on the "Columns in Comparison" column next to a table on the "Tables and Views" tab and removing some of the columns.

If you're running out of space you can change the location that SQL Data Compare uses for it's temp directory. Right click on "My Computer" and choose Properties
On the advanced tab then choose environmental variables button
Then under user or system variables click NEW and give the variable name as RGTEMP and the variable value as the path you want Red Gate SQL Compare and Data Compare to use as their temp directory.

Please note that version 7 of the Data Compare software can compress the temporary storage files, so the requirements will be less. The savings in terms of space used will depend on the type of data being stored.

Document ID: KB200705000041 Keywords: Data, Compare, disk, space, cache, low, filter, TMP, temp

Was this article helpful?

Search support