All Oracle Error Codes
Oracle DBA Forum

Frequent Oracle Errors

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


Richard Foote


Hi Syed,

It's a totally meaningless formula. Totally.

What governs how much PGA you require ? Two things. The total *number* of
concurrent sessions and what those sessions *do*. If your OLTP database runs
relatively few pieces of "code" on a small subset of data but requires
thousands of concurrent sessions, then it's quite conceivable you'll need a
significant proportion of your memory for PGA, more so than SGA. In fact,
large numbers of concurrent sessions will require mucho PGA, period.

Therefore, any "formula" that doesn't consider the concurrent activity of
the database is useless ...

One OLTP database I look after has approx. 50% memory for PGA, another has
5%. Go figure ?

The below quote was written by the same person that said a family requires a
house with 20% space for bedrooms and 80% for living space. Ask our
neighbours with 11 children to comply with the above "formula".

You get the picture.


----- Original Message -----
From: <SJHussain@(protected)>
To: <oracle-l@(protected)>
Sent: Tuesday, August 24, 2004 6:29 PM


I was just read Oracle Metalink Note 223730.1 Automatic PGA Memory
Management in 9i. There is a recommended formula for setting PGA on OLTP
and DSS systems. I am interested in OLT system only.
For OLTP the folurma is PGA_AGGREGATE_TARGET = (<Total Physical Memory> *
80%) * 20%

I just want to ask you people, how accurate is this formula?

Best Regards,

Syed Jaffar Hussain

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