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TNS:could not resolve the connect identifier specified
Backtrace message unwound by exceptions
invalid identifier
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end-of-file on communication channel
TNS:listener unknown in connect descriptor
insufficient privileges
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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: difference between child and parent latches?

K Gopalakrishnan

2004-03-23

Replies:
Tanel:

You have hit the nail on its head. _kghdsisx_count defines the number
of sub-pools (or in other words, number of latches for shared pool)
inside the shared pool. This is introduded to have bigger shared pool
sizes without having a latch contention problem. But I have never seen
that working as expected :(


--- Tanel Poder <tanel.poder.003@(protected):
> > Not quite true. (at least starting from 9i). The shared pool is
> > divided
> > in to multiple sub-pools if it is greater than 250MB and/or if your
> > cpu_count > 4. In this case the shared pool is covered by multiple
> > shared pool latches.
>
> I use my chance here to throw in an undocumented parameter
> _kghdsidx_count, which you could modify to manually control into how
> many heaps shared pool will be divided.
>
> Each heap has it's own freelist and lru lists and the latch
> protecting operations on them, this means you could relieve shared
> pool latch contention in extremely poorly written applications, but
> also you might introduce unnecessary ORA-4031 problems, when most
> allocations happen to be non-uniformly distributed to some specific
> heap resulting in out of memory error, while others heaps have might
> have enough (but unusable) space in them..

Very true. Recently I had the same problem with shared pool was erring
with 4031 for 2k chunks though the freepsace inside shared pool was
more than 400 MB (the shared pool was set to 1.6G for a 10 thousand
sessions) and the culprit was sub pools. Once we reduced the subpools
lower value from 7, the problem vanished :)

So it is good to have multiple sub pools, but the results may vary :)




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