Fernanda,

unless each of the portals do not have thousands of pages, it should be no problem. Anyway, each portal needs resources, so maybe your performance issue is a result of having too less RAM installed on your server, slow harddisks etc. Try using Windows and SQL Server performance monitoring tools to find the problem.

But first of all look at your event log and search index tables. If they get (too) big, truncate them.
Open Host :: SQL and enter the following commands (first block for event logs, second for search index):

TRUNCATE TABLE {databaseOwner}{objectQualifier}ScheduleHistory
TRUNCATE TABLE {databaseOwner}{objectQualifier}Eventlog
TRUNCATE TABLE {databaseOwner}{objectQualifier}Sitelog

TRUNCATE TABLE {databaseOwner}{objectQualifier}SearchItemWordPosition
DELETE {databaseOwner}{objectQualifier}SearchItemWord
DELETE {databaseOwner}{objectQualifier}SearchWord
DELETE {databaseOwner}{objectQualifier}SearchItem

Check "Run as script" and click the "Run script" button.

Best wishes
Michael

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