Hello,

Our app rebuilds indexes periodically (about once a month) by calling
"ALTER INDEX index_name ACTIVE" on a bunch of indexes in the database.
I need to estimate how much free disk space the customer should have
in order to complete this process. I decided to restrict
TempDirectories size, run the command and see when it starts failing.

Here are my findings:

1. TempDirectories = C:\Temp\Firebird
Running "ALTER INDEX idx_physical_copy_commit_number ACTIVE" succeeds

2. TempDirectories = C:\Temp\Firebird 100000000000
Running "ALTER INDEX idx_physical_copy_commit_number ACTIVE" causes
"GDS Exception. 335544675. sort error"

The database size is 1.5GB so 100 GB should be more than enough to
activate any index, right?

My main question is how can we calculate the temp sort space required
to ALTER INDEX ACTIVE (on all indexes serially) given the size of the
database? Is twice the size of the database a good upper bound? We
will provide this as a recommendation to our customers, so it has to
be simple :)

Thanks,

Alec