PGA memory problem - Oracle 10.2.0.4 on windows 2003

Question

Hi,
I have recently started work at a new company and we are running Oracle 10g (10.2.0.4, Enterprise Edition) on Windows 2003 (Standard Edition). The server has 4Gb of RAM (and we have modified boot.ini to inclue the /3Gb switch).
RE: SGA/PGA, we have the following Oracle parameters set:
sga_target 1G
pga_aggregate_target 194M
The employees tell me that they frequently "have to reboot the database" because of ORA-4030 and ORA-4031 problems. Looking at taskmgr on the server, Oracle is using "too much" memory (~3Gb). New sessions cannot connect etc. and they restart the database. Being a DBA (experience in UNIX, not Windows) I'm not so keen on this "solution" and am trying to find out what's happening.
When this problem occurred yesterday, before allowing the reboot, I bought myself some time to have a little dig around in the database. In v$sesstat I saw one process that had a value of over 1GB for "session pga memory". Memory usage on the server for oracle.exe was (as predicted) ~1GB over the "expected" 1.2Gb value (of SGA+PGA agg target). So, part 1 of my question is:
- Is this "normal" behaviour for Oracle to allow a process to go so wild on the PGA?
(I understood that Oracle would attempt to maintain total PGA memory close to the value of PGA_AGGREGATE_TARGET. I believe I read in the documentation that it could allow PGA memory to increase "up to 20% over this value" but please don't quote me on that, I can't find it again..)
Part 2 to this problem is that sessions "collect" in the database and do not release their PGA memory, leading to the slow build up of memory until the errors are encountered. I believe Dead Connection Detection (DCD) not to be working here (sql_net.expire_time=1 is set on the server but appears to do nothing). I've started reading docs/notes on this and it seems that DCD is not reliable on Windows. Metalink Doc 151972.1 suggests testing and adjusting some underlying TCP/IP serttings in the O/S kernel (I'm not even sure how to do this in Windows yet, let alone if it's something I want to get involved with!). So:
- I'm wondering if anyone has any tips for this (killing off dead connections, getting DCD working in Windows 2003 etc.)?  Any experiences, tips welcome here!!
Thanks in advance.
Regards,
Ados

Answer 1

user647632 wrote:
(By the way, can anyone recommend how to sort the formatting of these results please?!!)You can find all by clicking the Oracle Forum FAQ
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Here is my PGASTAT result. Have a look at the values.
SQL> column name  format a60
column value format 9,999,999,999,999,999
select * from gv$pgastat order by inst_id,name;
SQL> SQL>
   INST_ID NAME                                                                          VALUE UNIT
         1 PGA memory freed back to OS                                         202,362,322,944 bytes
         1 aggregate PGA auto target                                             1,831,209,984 bytes
         1 aggregate PGA target parameter                                        2,147,483,648 bytes
         1 bytes processed                                                     287,247,907,840 bytes
         1 cache hit percentage                                                             68 percent
         1 extra bytes read/written                                            133,790,002,176 bytes
         1 global memory bound                                                     214,743,040 bytes
         1 max processes count                                                              48
         1 maximum PGA allocated                                                 1,708,733,440 bytes
         1 maximum PGA used for auto workareas                                   1,112,871,936 bytes
         1 maximum PGA used for manual workareas                                       271,360 bytes
   INST_ID NAME                                                                          VALUE UNIT
         1 over allocation count                                                             0
         1 process count                                                                    42
         1 recompute count (total)                                                     136,756
         1 total PGA allocated                                                     328,158,208 bytes
         1 total PGA inuse                                                         196,502,528 bytes
         1 total PGA used for auto workareas                                        81,608,704 bytes
         1 total PGA used for manual workareas                                               0 bytes
         1 total freeable PGA memory                                                96,927,744 bytes
19 rows selected.
SQL>
SQL> column BYTES_PROCESSED format 9,999,999,999,999,999
column EST_RW_EXTRA_BYTES format 9,999,999,999,999,999
SQL> SQL> select inst_id,round(pga_target_for_estimate/1024/1024) as target_size_MB,
  2                bytes_processed,estd_extra_bytes_rw as est_rw_extra_bytes,
  3                estd_pga_cache_hit_percentage as est_hit_pct,
  4                estd_overalloc_count as est_overalloc
  5  from gv$pga_target_advice  order by inst_id,target_size_mb;
   INST_ID TARGET_SIZE_MB        BYTES_PROCESSED     EST_RW_EXTRA_BYTES EST_HIT_PCT EST_OVERALLOC
         1            256        285,418,388,480        188,648,610,816          60             4
         1            512        285,418,388,480        131,006,145,536          69             0
         1           1024        285,418,388,480         92,476,995,584          76             0
         1           1536        285,418,388,480         91,536,565,248          76             0
         1           2048        285,418,388,480         72,373,725,184          80             0
         1           2458        285,418,388,480         68,650,139,648          81             0
         1           2867        285,418,388,480         68,650,139,648          81             0
         1           3277        285,418,388,480         68,650,139,648          81             0
         1           3686        285,418,388,480         68,650,139,648          81             0
         1           4096        285,418,388,480         68,650,139,648          81             0
         1           6144        285,418,388,480         68,650,139,648          81             0
   INST_ID TARGET_SIZE_MB        BYTES_PROCESSED     EST_RW_EXTRA_BYTES EST_HIT_PCT EST_OVERALLOC
         1           8192        285,418,388,480         68,650,139,648          81             0
         1          12288        285,418,388,480         68,650,139,648          81             0
         1          16384        285,418,388,480         68,650,139,648          81             0
14 rows selected.
SQL>
SQL> show parameters pga
NAME                                 TYPE        VALUE
pga_aggregate_target                 big integer 2G
SQL> show parameters sga_max
NAME                                 TYPE        VALUE
sga_max_size                         big integer 2G
SQL> show parameters sga_target
NAME                                 TYPE        VALUE
sga_target                           big integer 2G
SQL>