The background of this issue is frequently bound to some cloning or copying some template database to a new instance.
The Oracle Support (former Metalink) for version 11.2.0.3 suggests to install patch "Patch 10110625: DBSNMP.BSLN_INTERNAL RECEIVES ORA-6502" or to recreate a DBSNMP user. However by googling I 've found more finesse solution -
https://oracledbazone.com/2012/04/17/ora-12012-error-on-auto-execute-of-job-sys-bsln_maintain_stats_job-2/.