update: Plus, thinking about it, in the situation you describe the A transaction should lock the sequence table until it is complete, and the B transaction would have to wait until A completed and removed the lock.
Sequences are an oracle construct that are NOT tables. You cannot lock a sequence. This is, in fact, the whole difference between a sequence and a table that you just select from, increment, and then update*. If sequences did behave transactionally, it would lead to lots of deadlock problems and MASSIVE inter-session contention (which is why you'd get so many deadlocks).
* in truth, it would be possible to implement an oracle sequence using a table, but only via another oracle-specific construct called an "autonomous subtransaction". An autonomous subtransaction is a transaction which commits or rolls back independantly of the transaction which invoked it. The point is, you *must* commit the incrementing of the sequence, *even if* you roll back the insert. Otherwise only one database session at a time would be able to have an open transaction inserting into a given table.
------------
:Wq
Not an editor command: Wq
-
Are you posting in the right place? Check out Where do I post X? to know for sure.
-
Posts may use any of the Perl Monks Approved HTML tags. Currently these include the following:
<code> <a> <b> <big>
<blockquote> <br /> <dd>
<dl> <dt> <em> <font>
<h1> <h2> <h3> <h4>
<h5> <h6> <hr /> <i>
<li> <nbsp> <ol> <p>
<small> <strike> <strong>
<sub> <sup> <table>
<td> <th> <tr> <tt>
<u> <ul>
-
Snippets of code should be wrapped in
<code> tags not
<pre> tags. In fact, <pre>
tags should generally be avoided. If they must
be used, extreme care should be
taken to ensure that their contents do not
have long lines (<70 chars), in order to prevent
horizontal scrolling (and possible janitor
intervention).
-
Want more info? How to link
or How to display code and escape characters
are good places to start.
|