Oracle SQL
  • LICENSE

Category Archives: remote statements

How to find out session info about session that comes from remote database through dblink

Posted on July 25, 2014 by Sayan Malakshinov Posted in oracle, remote statements, SQL*Plus 6 Comments

It is well known thing and you can even find it on MOS, but I have a little more simple script for it, so I want to show little example.

First of all we need to start script on local database:

SQL>                                                                                                                                                                   
SQL> @transactions/global.sql
Enter filters(empty for any)...
Sid           :
Globalid mask :
Remote_db mask:

 INST_ID  SID    SERIAL# USERNAME REMOTE_DB REMOTE_DBID TRANS_ID         DIRECTION   GLOBALID                                           EVENT                      
-------- ---- ---------- -------- --------- ----------- ---------------- ----------- -------------------------------------------------- ---------------------------
       1  275       4469 XTENDER  BAIKAL     1742630060 8.20.7119        FROM REMOTE 4241494B414C2E63616336656437362E382E32302E37313139 SQL*Net message from client
                                                                                                                                                                  

Then we need to copy GLOBALID of interested session and run script on database that shown in column REMOTE_DBID, but with specifieng GLOBALID:

SQL>                                                                                                                                                                                                 
SQL> conn sys/syspass@baikal as sysdba
Connected.

======================================================================
=======  Connected to  SYS@BAIKAL(baikal)(BAIKAL)
=======  SID           203
=======  SERIAL#       38399
=======  SPID          6536
=======  DB_VERSION    11.2.0.4.0
======================================================================

SQL> @transactions/global.sql
Enter filters(empty for any)...
Sid           :
Globalid mask : 4241494B414C2E63616336656437362E382E32302E37313139
Remote_db mask:

INST_ID   SID    SERIAL# USERNAME  REMOTE_DB  REMOTE_DBID TRANS_ID   DIRECTION   GLOBALID                                            STATE                     
------- ----- ---------- --------- ---------- ----------- ---------- ----------- --------------------------------------------------  --------------------------
      1     9      39637 XTENDER   BAIKAL      1742630060 8.20.7119  TO REMOTE   4241494B414C2E63616336656437362E382E32302E37313139  [ORACLE COORDINATED]ACTIVE

It’s quite simple and fast.

dblink global transaction remote sessions

Deceptive commit after select from dblink.

Posted on October 13, 2012 by Sayan Malakshinov Posted in commit, documentation, oracle, remote statements, trace, transactions Leave a comment

Recently on our russian forum we discussed about distributed transaction: is “insert /*+ append */ into x select * from t@dblink” a distributed transaction or not?
According to the documentation – no:

A distributed transaction includes one or more statements that, individually or as a group, update data on two or more distinct nodes of a distributed database

And Tom Kyte said the same:

In the following, we do not have a distributed transaction when we just insert /*+ append */ into local_table select * from remote@table; – we just have a single site transaction.

But v$global_transaction(but v$transaction), another part of documentation and v$lock(type=’DX’) assure that it is.

Distributed statement: A statement that accesses data on two or more distinct nodes/instances of a distributed database.
A remote statement accesses data on one remote node of a distributed database.

Who is right?

But it not so interesting as my another finding: commit after simple “select * from dblink” would be “read-only” commit on local db, but on remote it became “read-only” rollback! Except cases when there was any dml in that transaction(with no difference local or not). But how Oracle determining: read-only or not, execute commit or rollback?

Yet another interesting thing: If we do a few times “commit” after “select from dblink”, then, as expected, rollback will be executed only once on remote. But when we closing our session, there is another commit on remote(real read-only commit).

Tests below: Continue reading→

commit distributed transactions remote statements rollback
photo Sayan Malakshinov

Oracle ACE Pro Oracle ACE Pro

DEVVYOracle Database Developer Choice Award winner

Oracle performance tuning expert

UK / Cambridge

LinkedIn   Twitter
sayan@orasql.org

Recent Posts

  • CBO and Partial indexing
  • Slow index access “COL=:N” where :N is NULL
  • Where does the commit or rollback happen in PL/SQL code?
  • :1 and SP2-0553: Illegal variable name “1”.
  • ORA exceptions that can’t be caught by exception handler

Recent Comments

  • Oracle SGA 값을 증가 시킬 때 발생 장애 원인 – DBA의 정석 on Example of controlling “direct path reads” decision through SQL profile hints (index_stats/table_stats)
  • Oracle SQL | Oracle diagnostic events — Cheat sheet on Where does the commit or rollback happen in PL/SQL code?
  • Functions & Subqueries | Oracle Scratchpad on Deterministic function vs scalar subquery caching. Part 3
  • Materialized views state turns into compilation_error after refresh - kranar.top - Answering users questions... on Friday prank: select from join join join
  • Exadata Catalogue | Oracle Scratchpad on When bloggers get it wrong – part 1
  • Exadata Catalogue | Oracle Scratchpad on Serial Scans failing to offload
  • lateral join – decorrelation gone wrong – svenweller on Lateral view decorrelation(VW_DCL) causes wrong results with rownum
  • 255 column catalogue | Oracle Scratchpad on Intra-block row chaining optimization in 12.2
  • 255 column catalogue | Oracle Scratchpad on row pieces, 255 columns, intra-block row chaining in details
  • opt_estimate catalogue | Oracle Scratchpad on Correct syntax for the table_stats hint

Blogroll

  • Alex Fatkulin
  • Alexander Anokhin
  • Andrey Nikolaev
  • Charles Hooper
  • Christian Antognini
  • Coskan Gundogar
  • David Fitzjarrell
  • Igor Usoltsev
  • Jonathan Lewis
  • Karl Arao
  • Mark Bobak
  • Martin Bach
  • Martin Berger
  • Neil Chandler
  • Randolf Geist
  • Richard Foote
  • Riyaj Shamsudeen
  • Tanel Poder
  • Timur Akhmadeev
  • Valentin Nikotin

Meta

  • Log in
  • Entries feed
  • Comments feed
  • WordPress.org
©Sayan Malakshinov. Oracle SQL