strange (maybe) behaviour of table lock

I have a question regarding a strange behaviour (for me, maybe that this
is desidered feature) of LOCK on tables. I am using postgres 8.2

I have a servlet that uses connection pools.
The servlet do "LOCK table,table2,table3,table4"
then do some select (I am testing the code, I will put the update in the
future) an then I close instruction and connection.

The first 4 executions of the servlet goes well, the 5th hangs.
Afther that I use "psql" to do the last query (the one that hangs the
system) of the servlet, also psql hangs.

I did a modify of the servlet
"LOCK table,table2,table3,table4 IN EXCLUSIVE MODE" and no other
modifications. I stop and restart my system, all works well.

Can someone tell me if this is a desidered behaviour? (and if is
possible why). If may help I can post all the queryes and table
structure, they are a little long.

Thank you
Edoardo Panfili

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