Heap Dump

Heap dumps show details about the memory allocation and distribution in the shared pool and library cache including the details about the objects. It will also show the details about the cursors and the latch information when level 2 is used. It will have the details about the memory chunks (free, freeable, permanent, and recreatable) and their sizes. It will also have the information about the hash buckets and freelists inside the shared pool. Heap dumps are often requested by Oracle Support to diagnose shared pool related errors.

Syntax

Following methods show how to produce a heap dump.

Using ALTER SESSION

The first ALTER SESSION below will immediately produce a heap dump at supplied level number, while the second ALTER SESSION command will produce the heap dump when the session encounters ORA-4031 error.

 alter session set events 'immediate trace name heapdump level <level>'; 
 alter session set events '4031 trace name heapdump level 2'; 

Using oradebug

The following oradebug command sequence shows how to produce an immediate heap dump at level 10.

 oradebug setmypid 
 oradebug unlimit 
 oradebug dump  heapdump <  level  > 

Controlling the Dump Information Using Levels

The decimal value of shown in the following table can be used as level to control the dump information written to the trace file.

Heap	Hex	Dec
PGA	0x01	1
SGA	0x02	2
UGA	0x04	4
Current call	0x08	8
User call	0x10	6
Large pool	0x20	32

Example Output

The following snippet is from a trace file of the heap dump taken at level 2:

 HEAP DUMP heap name="sga heap"  desc=02E1DE80 
 extent sz=0x32c8 alt=104 het=32767 rec=9 flg=-126 opc=0 
 parent=00000000 owner=00000000 nex=00000000 xsz=0x0 
 ****************************************************** 
 HEAP DUMP heap name="sga heap(1,0)"  desc=04766E28 
 extent sz=0xfc4 alt=104 het=32767 rec=9 flg=-126 opc=0 
 parent=00000000 owner=00000000 nex=00000000 xsz=0x400000 
 EXTENT 0 addr=14000000 
 Chunk 1400002c sz=       24  R-freeable  "reserved stoppe" 
 Chunk 14000044 sz=   212900  R-free      "               " 
 Chunk 14033fe8 sz=       24  R-freeable  "reserved stoppe" 
 Chunk 14034000 sz=  3959460    perm      "perm           "  alo=3959460 
 Chunk 143faaa4 sz=    12172    perm      "perm           "  alo=12172 
 Chunk 143fda30 sz=     7792    perm      "perm           "  alo=7792 
 Chunk 143ff8a0 sz=       24    freeable  "service names a" 
 Chunk 143ff8b8 sz=       32    recreate  "fixed allocatio"  latch=130F87AC