Change Sessions on 10g database

Processes—In this field, specify the maximum number of processes that can
simultaneously connect to the database. Enter a number or accept the default
value of 150. The default value for this parameter is appropriate for many
environments. The value you select should allow for all background processes,
user processes, and parallel execution processes.

Specifying the Maximum Number of Processes
The PROCESSES initialization parameter determines the maximum number of
operating system processes that can be connected to Oracle Database concurrently. The
value of this parameter must be a minimum of one for each background process plus
one for each user process. The number of background processes will vary according
the database features that you are using. For example, if you are using Advanced
Queuing or the file mapping feature, you will have additional background processes.
If you are using Automatic Storage Management, then add three additional processes
for the database instance.
If you plan on running 50 user processes, a good estimate would be to set the
PROCESSES initialization parameter to 70.

It is all, i don't find about the relation of the value of processes and sessions.

How change "sessions" parameter when spfile?

I am not a user of XE but I believe, the command should work.

alter system set sessions=whatever_number_youwant scope=spfile;

After this give a restart and see.

If this doesn't work, create the pfile using the command,

create pfile from spfile;

Do the changes and than restart the db using the pfile.

 I have a server with version 10.2.0.1 and i defined 100 as value of processes and 80 as value in sessions.
My connections are dedicated and i shutdown the database and startup for apply the changes i see the following:

SQL> alter system set sessions=80 scope=spfile;

Sistema modificado.

SQL> alter system set processes=100 scope=spfile;

Sistema modificado.

shutdown immediate
startup

processes integer 100
sessions integer 115

Change Sessions, Transaction And Processes Parameters In Oracle 10g

alter system set PROCESSES=100 scope=SPFILE;

2.alter system set TRANSACTIONS=126 scope=SPFILE;

3.alter system set SESSIONS=115 scope=SPFILE;