| UL locks in Oracle Workspace Manager [message #240175] |
Thu, 24 May 2007 05:34 |
rokyta
Messages: 1
Registered: May 2007
Location: Czech Republic
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Junior Member |
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I have problems with blocking concurrent sessions when using Oracle Workspace Manager (OWM). OWM is used in one of our applications for a medium sized customer (about 100 concurrent users). The project data model contains foreign keys and is versioned using OWM upto the first level – thus there exists the LIVE workspace, and all child workspaces exist only on one level.
Problem No. 1 - OWM functions related to working with Workspaces lock the whole database instance against each other. For example the MergeWorkspace function blocks starting another MergeWS, CreateWS, or RemoveWS in any concurrent session that has been started from any scheme of the instance.
MergeWS also blocks the GotoWS function to a superior workspace, in the particular project GotoWS ('LIVE'), although according to the OWM documentation, a superior workspace should be in READ-ONLY mode and not completely locked when the MergeWS function is carried out.
Problem No. 2 - In addition, MergeWS blocks DML commands performed over versioned tables linked by a foreign key (FK).
Problem No. 3 - DML commands performed over versioned tables linked by a foreign key block each other.
It seems that either the referential integrity, or OWM can be used in Oracle – not both of them at the same time.
Problem No. 4 - When carrying out the RollbackToSavepoint function, it is possible to bring a deadlock relatively easily. However, this is one of the least important problems.
All mentioned locking events are “enq: UL-contention”, that means locks caused explicitly by Oracle Workspace Manager developers.
As for the customer, these problems result in such a situation that if any user starts MergeWS, the whole instance, of several tens to hundreds of users, is “frozen” for the period of several minutes and waits until the Merge ends. Neither another Merge nor GotoWS LIVE nor most of DML commands can be carried out.
Similarly, if the session works with versioned tables linked using foreign keys, the concurrent session working with identical tables can be blocked for several seconds or tens of seconds.
Although the behavior depends on the settings of various OWM parameters, for example the setting of “isrefreshed” when carrying out CreateWS , in my opinion this behavior conflicts in principle with both the OWM philosophy and its documentation. Therefore we have sent many Service Requests to Oracle Metalink, last Nos. 6237706.994 and 6312478.992.
I am ready to send you a set of scripts by means of which the monitored locks can be invoked simply.
Oracle responds – repeatedly - that it is a “feature” of the tool, not an error. The only mistake Oracle is willing to admit is the absence of these important facts in the OWM documentation.
I would like to ask whether any other users have similar experience with Oracle Workspace Manager, or can recommend resolving the situation, or if anybody knows another database environment able to provide solution similar to the OWM one but without those “features”.
Thank you.
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