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TNS:could not resolve the connect identifier specified
Backtrace message unwound by exceptions
invalid identifier
PL/SQL compilation error
internal error
missing expression
table or view does not exist
end-of-file on communication channel
TNS:listener unknown in connect descriptor
insufficient privileges
PL/SQL: numeric or value error string
TNS:protocol adapter error
ORACLE not available
target host or object does not exist
invalid number
unable to allocate string bytes of shared memory
resource busy and acquire with NOWAIT specified
error occurred at recursive SQL level string
ORACLE initialization or shutdown in progress
archiver error. Connect internal only, until freed
snapshot too old
unable to extend temp segment by string in tablespace
Credential retrieval failed
missing or invalid option
invalid username/password; logon denied
unable to create INITIAL extent for segment
out of process memory when trying to allocate string bytes
shared memory realm does not exist
cannot insert NULL
TNS:unable to connect to destination
remote database not found ora-02019
exception encountered: core dump
inconsistent datatypes
no data found
TNS:operation timed out
PL/SQL: could not find program
existing state of packages has been discarded
maximum number of processes exceeded
error signaled in parallel query server
ORACLE instance terminated. Disconnection forced
TNS:packet writer failure
see ORA-12699
missing right parenthesis
name is already used by an existing object
cannot identify/lock data file
invalid file operation
quoted string not properly terminated

Re: reading the SGA from my own program

Anjo Kolk


Not to be picky, but any query on the X$ or V$ (especially joins) will produce inconsistent results or data. That is the price that you pay. Now the big problem with reading SGA structures is with structures that are dynamic (v$session is not really dynamic), for example v$sqlarea. One needs to get a couple of latches to make sure that the pointers  are still valid (or are valid up to a certain point). Remember the good old days when SYSTEMSTATE dumps would coredump when executed on a live system? That is why it was a bad idea to have a backgroundprocess do a system state dump. One bad pointer and the instance is dead. So the other thing one can do if one can't use latches is to built in many checks to make sure the structures and addresses are still valid.

On 8/21/06, Powell, Mark D <mark.powell@eds.com> wrote:
The primary point of directly reading shared memory is that by doing so you bypass Oracle.  So when the entire instance hangs and will not grant new connections you can go around the problem and see what is happening (or not happening as the case may be).  You also avoid the latching overhead required for accessing the shared memory structures via Oracle.  True, you may see some inconsistent data, but you will see it.
HTH -- Mark D Powell --

From: oracle-l-bounce@freelists.org [mailto: oracle-l-bounce@freelists.org] On Behalf Of Allen, Brandon
Sent: Monday, August 21, 2006 12:25 PM
To: tanel.poder.003@mail.ee; anjo.kolk@oraperf.com; jeremiah@ora-600.net
Cc: Oracle Discussion List

Subject: RE: reading the SGA from my own program

Please forgive my ignorance, but what is the point of this direct SGA access anyway?  Why not just query v$session_event and/or v$session_wait, or the underlying x$ tables?

From: oracle-l-bounce@freelists.org [mailto: oracle-l-bounce@freelists.org] On Behalf Of Tanel Poder
Sent: Saturday, August 19, 2006 2:30 AM
To: anjo.kolk@oraperf.com
Cc: jeremiah@ora-600.net; 'Oracle Discussion List'
Subject: RE: reading the SGA from my own program
Also, if all you're interested in is the current wait state of a session, then there's no real fundamental need to map those SHM segments which do not contain the data you're interested in (as far as I understand).
. . . 

From: oracle-l-bounce@freelists.org [mailto: oracle-l-bounce@freelists.org] On Behalf Of Jeremiah Wilton
Sent: Saturday, August 19, 2006 05:14
To: 'Oracle Discussion List'
Subject: reading the SGA from my own program


I am trying to play around with reading the SGA using my own program, as popularized by Kyle Hailey and Miladin Modrakovic's papers and presentations.  I am confused about where to find x$ksusecst (session wait) and other items in the fixed area.

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Anjo Kolk
Owner and Founder OraPerf Projects
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