Oracle Backup with RMAN, runs slowly

Experts, I have an Oracle Database version 11g Release 11.2.0.3.0 - 64bit Production With the Real Application Clusters and Automatic Storage Management.

Linux Red Hat operating system 2.6.18-348.12.1.el5.

Database name: dbname

Database size: 92 GB.

Problem: The execution of a script, to perform backups with RMAN, is executed in 4 hours 45 minutes. The problem is that during its execution, other processes that interact with the database are affected.

Tables receive DML statements (udpate / insert / delete) every moment, throughout the day.

I can see in the RMAN log, two critical moments:

Starting backup at 04-04-2017 04:33:59
channel dbname_backup_disk1: starting incremental level 1 datafile backup set
channel dbname_backup_disk1: specifying datafile(s) in backup set
input datafile file number=00017 name=file_name ....                                                                        
...   "here all files"                                                                         
channel dbname_backup_disk1: starting piece 1 at 04-04-2017 04:34:00
channel dbname_backup_disk1: finished piece 1 at 04-04-2017 07:22:47
piece handle=+RECOVERY/dbname/backupset/2017_04_04/nnndn1_dbname_level_0_0.2614.940394043 tag=DBNAME_LEVEL_0 comment=NONE
channel dbname_backup_disk1: backup set complete, ***elapsed time: 02:48:48***

y:

 Starting backup at 04-04-2017 07:46:20
 backup will be obsolete on date 04-07-2017 07:46:20
 archived logs required to recover from this backup will expire when this 
 backup expires
 channel dev1: starting compressed full datafile backup set
 channel dev1: starting piece 1 at 04-04-2017 07:46:21
 channel dev1: finished piece 1 at 04-04-2017 09:22:07
 piece handle=/backup/oracle/backup/DBNAME_940405581_6656_1 tag=TAG20170404T074620 comment=NONE
 channel dev1: backup set complete, ***elapsed time: 01:35:46***
 Finished backup at 04-04-2017 09:22:07

Could you please help me identify the key to the problem? to decrease the duration of the backup.

The lines below are a section of the main script, called backup.pl. It runs every day at 2:30 am Local Time (UTC -3)

RMAN> run {
    show all;
    CONFIGURE RETENTION POLICY TO RECOVERY WINDOW OF 1 DAYS;
    configure controlfile autobackup on;
    CONFIGURE CONTROLFILE AUTOBACKUP FORMAT FOR DEVICE TYPE DISK TO '+RECOVERY/DBTARGET/%F';
    CONFIGURE CHANNEL DEVICE TYPE DISK FORMAT '+RECOVERY/DBTARGET/%d_%t_%s_%p';
    allocate channel dbname_backup_disk1 device type disk;
    REPORT OBSOLETE;
    DELETE OBSOLETE;
    recover copy of database with tag 'dbname_LEVEL_0' until time 'sysdate-1';
    backup incremental level 1 cumulative copies=1 for recover of copy with tag 'dbname_LEVEL_0' database include current controlfile;
    backup archivelog all not backed up format '+RECOVERY/DBTARGET/%d_%t_s%s_s%p';
    backup current controlfile for standby;
    delete archivelog until time='sysdate-3';
    release channel dbtarget_backup_disk1;
    sql "create pfile=''/backup/oracle/backup/ros1or01-initdbtarget1-20170404.ora'' from spfile";
    }
    allocate channel for maintenance type disk;
    delete noprompt obsolete device type disk;
    CROSSCHECK BACKUP;
    CROSSCHECK DATAFILECOPY ALL;
    CHANGE ARCHIVELOG ALL CROSSCHECK;
    DELETE EXPIRED ARCHIVELOG ALL;
    REPORT OBSOLETE;
    DELETE OBSOLETE;
    release channel;
    run
    {
    CONFIGURE CONTROLFILE AUTOBACKUP FORMAT FOR DEVICE TYPE DISK TO '/backup/oracle/backup/%F';
    allocate channel dev1 device type disk format '/backup/oracle/backup/%d_%t_%s_%p';
    backup backupset completed after 'sysdate-3/24';
    backup as compressed backupset datafilecopy all noduplicates KEEP UNTIL TIME 'SYSDATE+3' logs;
    release channel dev1;
    CONFIGURE CONTROLFILE AUTOBACKUP FORMAT FOR DEVICE TYPE DISK TO '+RECOVERY/DBTARGET/%F';
     }
     quit
    using target database control file instead of recovery catalog
    RMAN configuration parameters for database with db_unique_name DBTARGET are:
    CONFIGURE RETENTION POLICY TO RECOVERY WINDOW OF 1 DAYS;
    CONFIGURE BACKUP OPTIMIZATION OFF; # default
    CONFIGURE DEFAULT DEVICE TYPE TO DISK; # default
    CONFIGURE CONTROLFILE AUTOBACKUP ON;
    CONFIGURE CONTROLFILE AUTOBACKUP FORMAT FOR DEVICE TYPE DISK TO '+RECOVERY/DBTARGET/%F';
    CONFIGURE DEVICE TYPE DISK PARALLELISM 1 BACKUP TYPE TO BACKUPSET; # default
    CONFIGURE DATAFILE BACKUP COPIES FOR DEVICE TYPE DISK TO 1; # default
    CONFIGURE ARCHIVELOG BACKUP COPIES FOR DEVICE TYPE DISK TO 1; # default
    CONFIGURE CHANNEL DEVICE TYPE DISK FORMAT  '+RECOVERY/DBTARGET/%d_%t_%s_%p';
    CONFIGURE MAXSETSIZE TO UNLIMITED; # default
    CONFIGURE ENCRYPTION FOR DATABASE OFF; # default
    CONFIGURE ENCRYPTION ALGORITHM 'AES128'; # default
    CONFIGURE COMPRESSION ALGORITHM 'BASIC' AS OF RELEASE 'DEFAULT' OPTIMIZE FOR LOAD TRUE ; # default
    CONFIGURE ARCHIVELOG DELETION POLICY TO NONE; # default
    CONFIGURE SNAPSHOT CONTROLFILE NAME TO '/cots/oracle/11.2.0/dbhome_1/dbs/snapcf_dbtarget1.f'; # default

Thanks in advance.