We recently encountered a problem using the postgres-xl software, there is a table we can not drop can not alter, will always be in the execution state. We checked the Internet, and some answered that the table is locked, but the lifting of the lock Table or can not drop and alter. There are also replied that there is no transaction submitted, we use the sql statement can be found to have not submitted the transaction, but it can not rollback and commit, said the transaction does not exist.
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I have a table that is dropped every day and then recreated.
I executed some audit actions on that table (select, update, delete, insert, all).
Now I want to use the noaudit command to disable audit, but the table is already dropped, so I get an object does not exist exception.
When this table is recreated, will the audit work on it?
I have version oracle 11g.
Thanks.
in my pl\sql process, there is an execution of "alter table exchange parition.."
on some table.
the problem is that during that operation - other users can try to access the target table.
one process that executed a select query on that table, got this error:
ORA-08103 object no longer exists.
i think that it is not the same like 'object or view doesn't exist'.
i think that 'object no longer exists' error, come when the process start ok,
and then the exchange (or other operation) come from the side and the process
can't bo done.
the chance is very low that it will happen, because the exchange is very very fast.
but for this case, there is any idea how to solve it? how to prevent this situation?
maybe a way to execute the exchange only if no-one touch the table?
thanks.
This will happen when session #2 alters the table in the table after session #1 has opened its cursor but before it is finished fetching the rows from that cursor.
I don't think there is a foolproof way to prevent the exchange from happening unless you are willing to change the code that other users are using to access the target table.
LOCK TABLE mytable IN EXCLUSIVE MODE will not wait for SELECT statements to complete, nor will it prevent new SELECT statements from starting, so acquiring an exclusive lock before attempting the ALTER TABLE will not work.
If you want to prevent the ALTER TABLE from happening at the same time as SELECTs, you need both to depend on acquiring the same lock. A relatively robust way to do that would be to use the DBMS_LOCK package to allocate a lock for that table. Call that lock "mytablelock".
Then, using DBMS_LOCK, your SELECT sessions would need to acquire "shared" locks on "mytablelock" before progressing. Your alter table sessions would need to acquire an "exclusive" lock on "mytablelock" before progressing.
This scheme would allow multiple SELECT sessions to run without interfering with each other, but it would prevent the ALTER TABLE from running while any SELECT was running.
A (much) less robust, but simpler, way to do it would be to change the SELECT statements issued from the other query into SELECT FOR UPDATES. But that's a recipe for lots of unnecessary waits and deadlock errors.
We have a daily partitioned table with retention of about 180 days. We have created a view with a group by .., to_char(DATE_COL,'YYYYMM');
The users started to extract the data from the views for each month; and at one moment of executing the view for 201510, it had failed with "Object no longer exists" even though the view and the underlying table exists.
I am suspecting that Unix issued a new partition creation statement for the next day which is automated process(verified in data dictionary);
The question is if the query on the view is running, there would be read lock on the table, thereby the partition couldn't have been created as it needs exclusive lock;
If the view wasn't running, then the ALTER table statement to create partition would have been completed and then if there was any query on the view, it wouldn't have been failed.
Did the query on the view fired at almost the same time when alter table statement to add partition was being executed; if so, as there is an exclusive lock on the table through alter table statement, the query on the view would have waited for read lock as currently there is exclusive lock. Why did I see this error, can you please elucidate.
When I want to update, delete, insert I need to commit. That's helpful most of the time, I might update wrong information or delete something by mistake and I can undo that.
When dropping a column, I don't need a commit. Is there something like rollback (not flashback), which enables me to undo my changes quickly? Dropping a column, even after a long analysis can probably cause damage to the table (pk, fk).
Why did Oracle provided a commit for DML but not for DDL?
Why did Oracle provided a commit for DML but not for DDL?
When you issue a DDL statement, you basically start a transaction against the Oracle data dictionary, and this transaction, to eliminate any overheads, has to be as short as possible and take effect as soon as possible. Because of this, DDL statement does double commit, before the DDL statement and then right after(or rollback, if something went wrong) the statement. This behavior makes Oracle's DDL not transactional DDL and you cannot commit or rollback it explicitly. It's just the way it is.
Having said that, if you dropped a table, then starting from 10g and up you can use flashback table technology to get it back in one statement, because Oracle, after you issue drop table statement wont drop it, it rather puts it in the recycle bin:
flashback table <<table_name>> to before drop
Unfortunately you cannot use flashback table, to restore a dropped column of a table, simply because dropped column wont be placed in the recycle bin. You will have to perform a point in time recovery of your full database or a single tablespace, or if there is a logical backup(*.dmp file), restore table from it by using imp or impdp utility.
I am keeping two passwords (actually the same password as far as website human user knows,but hashed and salted using two different algorithms and salts) for my website. One is place in WebUsers table and that is where password is verified when users login at website. The other is password of an oracle user, each website user corresponds to an oracle user.
When making change password procedure, I have to change password in WebUsers table as well as in oracle, in a transaction. The problem is, the DDL statement [alter user ...] commit before performing any action. If [alter user ...] fail and in the exception handling code I rollback the transaction, the changes in the WebUsers table are not rollbacked. Is there some work around?
There is just no way to have a DML and DDL in one atomic transaction under Oracle.
In Oracle a a DDL will always explicitly result in a commit before running the DDL.
Typically in these sort of scenarios, you should execute the step that's most likely to fail first, i.e. in your case the DDL 'Alter User'.
And then run your DML , only if the DDL succeeds , but then again, there is this issue of the DML failing, and then not being able to rollback the DDL, at which point you'll simply have to run another DDL to revert the changes made by the first DDL.
The idea is that the second step is far more likely to fail than the first step.
This pattern is also used, where you've to deal with say something like JMS + JDBC , and you can't use a JTA transaction to wrap the JMS + JDBC activities in a single transcation.