Server-side processing
Server-side processing allows you to set up a report that performs the majority of its processing on the server and pushes only relevant details to your computer.

Server-side processing provides you with a number of benefits:

Less time connected to the server. 
Less memory needed to process the report on your computer. 
Lower transfer time from the server to the client. 

Here's how server-side processing works: by using SQL pass-through technology to send an SQL statement to the database server and retrieve an initial set of data, Crystal Reports off-loads much of the data retrieval and sorting work onto the server system, thus freeing up local memory and resources for more important tasks. That is why server-side processing works only for reports that have been sorted and grouped; if a report has not been sorted and grouped (for example, if it is a simple list report), then there is no processing to push to the server. You should also note that server-side processing works only for reports based on SQL data sources.

Note:    

This description applies only to off-loading grouping and sorting to the server. 
Large amounts of server resources can be used for the temporary databases required when pushing grouping to the server. 
Keep in mind that in order to perform the grouping on the server, your report must conform to the following conditions:

The Perform Grouping on Server option (in the Options dialog box) is enabled. For more information, see Enabling server-side processing. 
The report uses some form of grouping. 
The report is at least partially hidden (at the very least, the Details section must be hidden). Since the server will process those sections that are hidden, the greater the portion of the report that is visible, the greater the amount of processing that must take place on the client side. If the Details section is shown, server-side processing will not be possible. 
In some cases, formula fields must be processed on the client side. If grouping is based on a formula field, or if a formula is used in a summary field, then all the records must be transferred to the client side before the formula can be evaluated. This will increase the amount of time required to run the report. Therefore, you may want to use SQL expressions as an alternative to formulas. 
Note:    Formulas used for record selection are an exception and can be pushed down to the server.

For a report to be processed on the server, any running totals appearing in the report must be based on summary fields (since the data needed for the running totals will be pulled over to the client side). 
For a report to be processed on the server, the report must contain only summary fields of these types: Sum, Maximum, Minimum, Count. 
The report does not contain specified value grouping. 
Note:    

When you drill-down on a hidden section of a report, with the processing being done on the server, connection to the server will be automatically initiated. If the client is disconnected from the server (for example, if you download a report onto your laptop and you work on it from a remote location), then drilling-down on data will produce an error since the database is not available. 
If you save a report that has been partially processed on the server using the Save Data with Report option, the program will save only those records that have been transferred to the client side. In other words, if you have drilled-down on a hidden section and there is a tab for that data in Crystal Reports (indicating the data has been transferred), those records will be saved with the report.