Package execution time increases with time

There is a package in our production database whose performance (execution time) degrades over time. Please find below details of execution time as time goes on:

Oracle Database Version: 11.2.0.2.0

Platform: Solaris 5.10

No. of Hours after Application is started     Average Execution Elapsed Time (seconds)          No. of Executions

-------------------------------------------------------     -----------------------------------------------------------------          ------------------------

1                                                          1.6                                                                           1096

2                                                           2.6                                                                          1019

3                                                           3.2                                                                           995                 

4                                                           3.1                                                                           1074

5                                                           4.1                                                                           1035

6                                                           6.7                                                                           741

7                                                           7.5                                                                           823   

8                                                           5.5                                                                           716

9                                                           8.9                                                                           549

10                                                         8.4                                                                           914

The general trend is that execution time continues to increase until we restart the Weblogic Application that executes this package; and then the cycle is repeated again.

Weblogic Version: 10.3.2

Could this be caused by a Bug or an insufficient/inappropriate Database setting?

I need help please.

Thanks