I have received below error on one of the 10gR2 database.
ORA-07445: exception encountered: core dump [kohfrem()+145] [SIGSEGV] [Address not mapped to object] [0x2B69FFFFFFF8]  
ORA-04030: out of process memory when trying to allocate 16408 bytes (koh-kghu sessi,pmucpkl kolctx)
If user or application running many jobs then the processes running the jobs may use an increasing amount of memory over time and the job queue process may fail with ORA-4030 errors.
In that case you might be hitting a bug 7715994 and refer below Metalink note
Bug 7715994 Memory leak / ORA-4030 when running many jobs
The bug has been fixed in 22.214.171.124. After spending many hours I found below workaround
Work around: When running large numbers of jobs, restart the session occasionally.
If user or application using UTL_FILE package then you see a constant growth of memory & the heapdumps suggest "koh-kghu sessi" heap is growing as a part of allocating chunks marked with "pmucalm coll", then you might be hitting the bug 7197637.
Refer below metalink note
Bug 7197637: MEMORY LEAK LEADING TO ORA-4030 (KOH-KGHU SESSI,PMUCALM COLL) USING UTL_FILE
The affected Oracle versions with this bug are 10.2.0.4 and 126.96.36.199 and it is fixed in 11gR2.
Workaround: Do not open too many files.
NOTE that users might expose Bug 9928290 due to regression exposed in the bug fix 7197637 and it is advised to apply both patches to fix the issue. But patch 9928290 is available from version 10.2.0.4.4
If your database running in <= 10.2.0.4.4 then you need to choose one of the below options.
1. Upgrade the database to 10.2.0.5 (using patch 8202632) and apply patches 9928290, 7197637
2. Upgrade the database to 10.2.0.4.4 PSU (using patch 9352164) and apply patches 9928290, 7197637
There are many bugs caused by this error. Check below metalink note for known bugs and possible actions in various versions
OERR: ORA 4030 "out of process memory when trying to allocate %s bytes (%s,%s)"
Please note that there are different errors across the various versions. I would recommend checking the Look-up Tool to find the Actual Cause and Possible solutions and contact Oracle Support.
ORA-600/ORA-7445/ORA-700 Error Look-up Tool [Article ID 153788.1]
Master Note for Diagnosing ORA-7445 and Related Core Dumps [Article ID 1092855.1]
Satishbabu Gunukula, Oracle ACE