Oraclue

Oracle internals, debugging and undocumented features

MMAN – memory broker statistics

Some background on memory broker:

The Automatic Shared Memory Management feature uses  background process named Memory Manager (MMAN).MMAN serves as the SGA Memory Broker and coordinates the sizing of the memory components. The SGA Memory Broker keeps track of the sizes of the components and pending resize operations.There is not so many document on this process but here is some help:

Let’s see what is MMAN responsible for :
SQL> select substr(DEST,1,10) DEST, DESCRIPTION from x$messages where DEST=’MMAN’;

DEST                           DESCRIPTION
—————————— ——————————————————–
MMAN                           lock memory at startup
MMAN                           lock memory timeout action
MMAN                           Memory Management
MMAN                           Complete deferred initialization of components
MMAN                           Handle sga_target resize
MMAN                           Handle mem_target resize
MMAN                           Handle sga_target deferred request delete
MMAN                           Reset advisory pool when advisory turned ON

The SGA Memory Broker keeps track of the sizes of the components and pending resize operations.

We can dump memory broker statistics into trace file using

oradebug dump DUMP_ADV_SNAPSHOTS  command e.g.
SQL> oradebug setmypid
SQL> oradebug dump DUMP_ADV_SNAPSHOTS 0

Default value for memory broker statistis is 30 sec.It is controled by underscore parameter

_memory_broker_stat_interval             30      memory broker statistics gathering interval for auto sga

and can be changed with alter system command e.g.

alter system set “_memory_broker_stat_interval”=60 scope=both sid=’demo1′; will change gathering interval to one minute.

New snapshot will be generated  after _memory_broker_stat_interval expires.

Trace file has various statistics for diffrent SGA components.Note snapshots numbers and timestamp.

Processing Oradebug command ‘dump DUMP_ADV_SNAPSHOTS 0’
Dumping memory broker statistics snapshots 5677
0: ———————————————————–
Stats Entry #5646 taken at timestamp 671200759
Stat                      Value
——————————-
DB time                   355973
DEFAULT cache read count  33608
DEFAULT cache read time   227
shared pool load count    24336
shared pool load time     53486
java pool load count      422
java pool load time       11
shared io pool wait time       0
Component              Granules
——————————-
DEFAULT cache          70
Shared Pool            33
Large Pool             1
Java Pool              2
SGA Target             107
PGA Target             72
Default Cache Advice Version=12 Start Index of Version=9
Default Cache Granules -> Estimated Read Time
———————————————–
———————————————–
7 -> 364, 14 -> 275, 21 -> 235, 28 -> 227, 35 -> 227, 42 -> 227, 49 -> 227, 56 -> 227, 63 -> 227, 70 -> 227, 77 -> 227, 84 -> 227, 91 -> 227, 98
-> 227, 105 -> 227, 112 -> 227, 119 -> 227, 126 -> 227, 133 -> 227, 140 -> 227
Shared Pool Advice Version=16 Start Index of Version=9
Shared Pool Granules -> Estimated Load Time
———————————————–
25 -> 3590, 29 -> 1856, 33 -> 195, 37 -> 1, 41 -> 1, 45 -> 1, 49 -> 1, 53 -> 1, 57 -> 1, 61 -> 1, 65 -> 1, 69 -> 1
Java Pool Advice Version=2 Start Index of Version=20
Java Pool Granules -> Estimated Load Time
———————————————–
1 -> 195, 2 -> 195, 3 -> 195, 4 -> 195
PGA Target Advice Version=1 Start Index of Version=0
PGA Granules -> Estimated PGA Processing Time
———————————————–
9 -> 11962649, 18 -> 11886641, 36 -> 11886641, 54 -> 11886641, 72 -> 11886641, 86 -> 11886641, 100 -> 11886641, 115 -> 11886641, 129 -> 11886641,
 144 -> 11886641, 216 -> 11886641, 288 -> 11886641, 432 -> 11886641, 576 -> 11886641
————————————————————-
1: ———————————————————–
Stats Entry #5677 taken at timestamp 671202561

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One response to “MMAN – memory broker statistics

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