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Old 11-30-2012, 02:31 AM   #1
thiyagusham
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Registered: Apr 2012
Posts: 213

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Semaphores allocation with IPCS


Hi to all;

1.Can semaphore allow two different process at a time?
2. Is there any Max limiy ?

I am trying to find how semaphores prevents two different processes at a time as well as checked semaphore array no's.
I updated two tables sententiously. Here , semaphores allowed two process updating table con currently.

1. Can anyone clear my confusion ?
Semephore allocated same arrays for two different processes but linux says semaphore allocates different arrays for each process. but in ouput not found different arrays.

PHP Code:
SQLshow user;
USER is "SONY"
SQLupdate tab3 set name='SONY';
200000 rows updated
PHP Code:
SQLshow user;
USER is "SONA"
SQLupdate tab4 set name='SONA';
200000 rows updated
>> Before UPDATE THE TABLE >>

PHP Code:
[oracle@localhost ~]$ ipcs

------ Shared Memory Segments --------
key        shmid      owner      perms      bytes      nattch     status
0xc2da0d04 458763     oracle    640        287309824  19

------ Semaphore Arrays --------
key        semid      owner      perms      nsems
0xd5f61564 229376     oracle    640        154

------ Message Queues --------
key        msqid      owner      perms      used-bytes   messages 
>> When updating tables >>
PHP Code:
[oracle@localhost ~]$ ipcs

------ Shared Memory Segments --------
key        shmid      owner      perms      bytes      nattch     status
0xc2da0d04 458763     oracle    640        287309824  19

------ Semaphore Arrays --------
key        semid      owner      perms      nsems
0xd5f61564 229376     oracle    640        154

------ Message Queues --------
key        msqid      owner      perms      used-bytes   messages 
>> After Updated the tables>>
PHP Code:
[oracle@localhost ~]$ ipcs

------ Shared Memory Segments --------
key        shmid      owner      perms      bytes      nattch     status
0xc2da0d04 458763     oracle    640        287309824  19

------ Semaphore Arrays --------
key        semid      owner      perms      nsems
0xd5f61564 229376     oracle    640        154

------ Message Queues --------
key        msqid      owner      perms      used-bytes   messages 
BEFORE , CURRENT , After ( table updation) why ipcs showing same
address here ?


Regards
Thiyagusham .G
 
  


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