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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: mysql

stephen booth

2005-04-04

Replies:
On Apr 4, 2005 7:11 PM, David <thump@(protected):
> What are the largest pros and cons involved in discussing mysql versus
> Oracle?

MySQL doesn't have the recoverability features of Oracle, you lose a
disk and you've lost everything since the last backup. WikiPedia
recently lost 2 days of updates when they lost a 'disk' (actually a
RAID arrary presented as a virtualdisk) with their MySQL data on, it
took them a day and a half to get up and running again. LiveJournal,
in January, didn't lose any data when their CoLo company lost power
but did take 3 days to get a working system back. They didn't lose
data because their middleware had features to make up for the lack in
MySQL. Still, a 3 day outage for a power loss of less than 1 hour is
really not good.

MySQL scaling is a joke. High volume sites (such as WikiPedia and
LiveJournal) scale by running many servers in paralell then
implementing bespoke replication and multiple master-slave (typically
reads go to the slaves and writes to the masters, periodically the
slaves pull updates from the Masters) clusters. This works well where
reads massively out number writes but quickly gets bottlenecked on
writes (as can be seen when trying to post a journal entry on
LiveJournal at peak times, it presents as a server busy error).

MySQL was originally developed by a supermarket (as I recall) for use
in daily reporting, essentially a datamart. The day's transactions
would be loaded in and summaries generated then the reports would be
run. If the database got fried then they still had the original files
so could rebuild it easily. All releases have carried that original
assumption forward. Not very suitable for OLTP use.

Stephen

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