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ActivePerl Documentation
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 DBD::Oracle - Oracle database driver for the DBI module


NAME

DBD::Oracle - Oracle database driver for the DBI module


SUPPORTED PLATFORMS

  • Windows
This module is not included with the standard ActivePerl distribution. It is available as a separate download using PPM.

SYNOPSIS

  use DBI;
  $dbh = DBI->connect("dbi:Oracle:$dbname", $user, $passwd);
  $dbh = DBI->connect("dbi:Oracle:host=$host;sid=$sid", $user, $passwd);
  # See the DBI module documentation for full details
  # for some advanced uses you may need Oracle type values:
  use DBD::Oracle qw(:ora_types);


DESCRIPTION

DBD::Oracle is a Perl module which works with the DBI module to provide access to Oracle databases (both version 7 and 8).


CONNECTING TO ORACLE

This is a topic which often causes problems. Mainly due to Oracle's many and sometimes complex ways of specifying and connecting to databases. (James Taylor and Lane Sharman have contributed much of the text in this section.)

Connecting without environment variables or tnsname.ora file

If you use the host=$host;sid=$sid style syntax, for example:

  $dbh = DBI->connect("dbi:Oracle:host=myhost.com;sid=ORCL", $user, $passwd);

then DBD::Oracle will construct a full connection descriptor string for you and Oracle will not need to consult the tnsname.ora file. If a port number is not specified then the descriptor try both 1526 and 1521 in that order.

Oracle environment variables

Oracle typically uses two environment variables to specify default connections: ORACLE_SID and TWO_TASK.

ORACLE_SID is really unnecessary to set since TWO_TASK provides the same functionality in addition to allowing remote connections.

  % setenv TWO_TASK T:hostname:ORACLE_SID            # for csh shell
  $ TWO_TASK=T:hostname:ORACLE_SID export TWO_TASK   # for sh shell
  % sqlplus username/password

Note that if you have *both* local and remote databases, and you have ORACLE_SID *and* TWO_TASK set, and you don't specify a fully qualified connect string on the command line, TWO_TASK takes precedence over ORACLE_SID (i.e. you get connected to remote system).

  TWO_TASK=P:sid

will use the pipe driver for local connections using SQL*Net v1.

  TWO_TASK=T:machine:sid

will use TCP/IP (or D for DECNET, etc.) for remote SQL*Net v1 connection.

  TWO_TASK=dbname

will use the info stored in the SQL*Net v2 tnsnames.ora configuration file for local or remote connections.

The ORACLE_HOME environment variable should be set correctly. It can be left unset if you aren't using any of Oracle's executables, but it is not recommended and error messages may not display.

Discouraging the use of ORACLE_SID makes it easier on the users to see what is going on. (It's unfortunate that TWO_TASK couldn't be renamed, since it makes no sense to the end user, and doesn't have the ORACLE prefix).

Connection Examples Using DBD::Oracle

Below are various ways of connecting to an oracle database using SQL*Net 1.x and SQL*Net 2.x. ``Machine'' is the computer the database is running on, ``SID'' is the SID of the database, ``DB'' is the SQL*Net 2.x connection descriptor for the database.

Note: Some of these formats may not work with Oracle 8.

  BEGIN {
     $ENV{ORACLE_HOME} = '/home/oracle/product/7.x.x';
     $ENV{TWO_TASK}    = 'DB';
  }
  $dbh = DBI->connect('dbi:Oracle:','scott', 'tiger');
  #  - or -
  $dbh = DBI->connect('dbi:Oracle:','scott/tiger');

works for SQL*Net 2.x, so does

  $ENV{TWO_TASK}    = 'T:Machine:SID';

for SQL*Net 1.x connections. For local connections you can use the pipe driver:

  $ENV{TWO_TASK}    = 'P:SID';

Here are some variations (not setting TWO_TASK)

  $dbh = DBI->connect('dbi:Oracle:T:Machine:SID','username','password')
  $dbh = DBI->connect('dbi:Oracle:','username@T:Machine:SID','password')
  $dbh = DBI->connect('dbi:Oracle:','username@DB','password')
  $dbh = DBI->connect('dbi:Oracle:DB','username','password')
  $dbh = DBI->connect('dbi:Oracle:DB','username/password','')
  $dbh = DBI->connect('dbi:Oracle:host=foobar;sid=ORCL;port=1521', 'scott/tiger', '')
  $dbh = DBI->connect('dbi:Oracle:', q{scott/tiger@(DESCRIPTION=
  (ADDRESS=(PROTOCOL=TCP)(HOST= foobar)(PORT=1521))
  (CONNECT_DATA=(SID=ORCL)))}, "")

If you are having problems with login taking a long time (>10 secs say) then you might have tripped up on an Oracle bug. You can try using one of the ...@DB variants as a workaround. E.g.,

  $dbh = DBI->connect('','username/password@DB','');

On the other hand, that may cause you to trip up on another Oracle bug that causes alternating connection attempts to fail! (In reality only a small proportion of people experience these problems.)

Optimizing Oracle's listner

[By Lane Sharman <lane@bienlogic.com>] I spent a LOT of time optimizing listener.ora and I am including it here for anyone to benefit from. My connections over tnslistener on the same humble Netra 1 take an average of 10-20 milli seconds according to tnsping. If anyone knows how to make it better, please let me know!

 LISTENER =
  (ADDRESS_LIST =
    (ADDRESS =
      (PROTOCOL = TCP)
      (Host = aa.bbb.cc.d)
      (Port = 1521)
      (QUEUESIZE=10)
    )
  )
 STARTUP_WAIT_TIME_LISTENER = 0
 CONNECT_TIMEOUT_LISTENER = 10
 TRACE_LEVEL_LISTENER = OFF
 SID_LIST_LISTENER =
  (SID_LIST =
    (SID_DESC =
      (SID_NAME = xxxx)
      (ORACLE_HOME = /xxx/local/oracle7-3)
        (PRESPAWN_MAX = 40)
        (PRESPAWN_LIST=
        (PRESPAWN_DESC=(PROTOCOL=tcp) (POOL_SIZE=40) (TIMEOUT=120))
      )
    )
  )

1) When the application is co-located on the host AND there is no need for outside SQLNet connectivity, stop the listener. You do not need it. Get your application/cgi/whatever working using pipes and shared memory. I am convinced that this is one of the connection bugs (sockets over the same machine). Note the $ENV{ORAPIPES} env var. The essential code to do this at the end of this section.

2) Be careful in how you implement the multi-threaded server. Currently I am not using it in the initxxxx.ora file but will be doing some more testing.

3) Be sure to create user rollback segments and use them; do not use the system rollback segments; however, you must also create a small rollback space for the system as well.

5) Use large tuning settings and get lots of RAM. Check out all the parameters you can set in v$parameters because there are quite a few not documented you may to set in your initxxx.ora file.

6) Use svrmgrl to control oracle from the command line. Write lots of small SQL scripts to get at V$ info.

  use DBI;
  # Environmental variables used by Oracle
  $ENV{ORACLE_SID}   = "xxx";
  $ENV{ORACLE_HOME}  = "/opt/oracle7";
  $ENV{EPC_DISABLED} = "TRUE";
  $ENV{ORAPIPES} = "V2";
  my $dbname = "xxx";
  my $dbuser = "xxx";
  my $dbpass = "xxx";
  my $dbh = DBI->connect("dbi:Oracle:$dbname", $dbuser, $dbpass)
             || die "Unale to connect to $dbname: $DBI::errstr\n";

Oracle utilities

If you are still having problems connecting then the Oracle adapters utility may offer some help. Run these two commands:

  $ORACLE_HOME/bin/adapters
  $ORACLE_HOME/bin/adapters $ORACLE_HOME/bin/sqlplus

and check the output. The ``Protocol Adapters'' section should be the same. It should include at least ``IPC Protocol Adapter'' and ``TCP/IP Protocol Adapter''.

If it generates any errors which look relevant then please talk to yor Oracle technical support (and not the dbi-users mailing list). Thanks. Thanks to Mark Dedlow for this information.

Connect Attributes

The ora_session_mode attribute can be used to connect with SYSDBA authorization and SYSOPER authorization.

  $mode = 2;    # SYSDBA
  $mode = 4;    # SYSOPER
  DBI->connect($dsn, $user, $passwd, { ora_session_mode => $mode });


International NLS / 8-bit text issues

If 8-bit text is returned as '?' characters or can't be inserted make sure the following environment vaiables are set correctly: NLS_LANG, ORA_NLS, ORA_NLS32, ORA_NLS33 Thanks to Robin Langdon <robin@igis.se> for this information. Example: $ENV{NLS_LANG} = ``american_america.we8iso8859p1''; $ENV{ORA_NLS} = ``$ENV{ORACLE_HOME}/ocommon/nls/admin/data'';

Also From: Yngvi Thor Sigurjonsson <yngvi@hagkaup.is> If you are using 8-bit characters and ``export'' for backups make sure that you have NLS_LANG set when export is run. Otherwise you might get unusable backups with ? replacing all your beloved characters. We were lucky once when we noticed that our exports were damaged before disaster struck.

Remember that the database has to be created with an 8-bit character set.

Also note that the NLS files $ORACLE_HOME/ocommon/nls/admin/data changed extension (from .d to .nlb) between 7.2.3 and 7.3.2.


PL/SQL Examples

These PL/SQL examples come from: Eric Bartley <bartley@cc.purdue.edu>.

  # we assume this package already exists
  my $plsql = q{
    CREATE OR REPLACE PACKAGE plsql_example
    IS
      PROCEDURE proc_np;
      PROCEDURE proc_in (
          err_code IN NUMBER
      );
      PROCEDURE proc_in_inout (
          test_num IN NUMBER,
          is_odd IN OUT NUMBER
      );
      FUNCTION func_np
        RETURN VARCHAR2;
    END plsql_example;
    CREATE OR REPLACE PACKAGE BODY plsql_example
    IS
      PROCEDURE proc_np
      IS
        whoami VARCHAR2(20) := NULL;
      BEGIN
        SELECT USER INTO whoami FROM DUAL;
      END;
      PROCEDURE proc_in (
        err_code IN NUMBER
      )
      IS
      BEGIN
        RAISE_APPLICATION_ERROR(err_code, 'This is a test.');
      END;
      PROCEDURE proc_in_inout (
        test_num IN NUMBER,
        is_odd IN OUT NUMBER
      )
      IS
      BEGIN
        is_odd := MOD(test_num, 2);
      END;
      FUNCTION func_np
        RETURN VARCHAR2
      IS
        ret_val VARCHAR2(20);
      BEGIN
        SELECT USER INTO ret_val FROM DUAL;
        RETURN ret_val;
      END;
    END plsql_example;
  };
  use DBI;
  my($db, $csr, $ret_val);
  $db = DBI->connect('dbi:Oracle:database','user','password')
        or die "Unable to connect: $DBI::errstr";
  # So we don't have to check every DBI call we set RaiseError.
  # See the DBI docs now if you're not familiar with RaiseError.
  $db->{RaiseError} = 1;
  # Example 1
  #
  # Calling a PLSQL procedure that takes no parameters. This shows you the
  # basic's of what you need to execute a PLSQL procedure. Just wrap your
  # procedure call in a BEGIN END; block just like you'd do in SQL*Plus.
  #
  # p.s. If you've used SQL*Plus's exec command all it does is wrap the
  #      command in a BEGIN END; block for you.
  $csr = $db->prepare(q{
    BEGIN
      PLSQL_EXAMPLE.PROC_NP;
    END;
  });
  $csr->execute;
  # Example 2
  #
  # Now we call a procedure that has 1 IN parameter. Here we use bind_param
  # to bind out parameter to the prepared statement just like you might
  # do for an INSERT, UPDATE, DELETE, or SELECT statement.
  #
  # I could have used positional placeholders (e.g. :1, :2, etc.) or
  # ODBC style placeholders (e.g. ?), but I prefer Oracle's named
  # placeholders (but few DBI drivers support them so they're not portable).
  my $err_code = -20001;
  $csr = $db->prepare(q{
        BEGIN
            PLSQL_EXAMPLE.PROC_IN(:err_code);
        END;
  });
  $csr->bind_param(":err_code", $err_code);
  # PROC_IN will RAISE_APPLICATION_ERROR which will cause the execute to 'fail'.
  # Because we set RaiseError, the DBI will croak (die) so we catch that with eval.
  eval {
    $csr->execute;
  };
  print 'After proc_in: $@=',"'$@', errstr=$DBI::errstr, ret_val=$ret_val\n";
  # Example 3
  #
  # Building on the last example, I've added 1 IN OUT parameter. We still
  # use a placeholders in the call to prepare, the difference is that
  # we now call bind_param_inout to bind the value to the place holder.
  #
  # Note that the third parameter to bind_param_inout is the maximum size
  # of the variable. You normally make this slightly larger than necessary.
  # But note that the perl variable will have that much memory assigned to
  # it even if the actual value returned is shorter.
  my $test_num = 5;
  my $is_odd;
  $csr = $db->prepare(q{
        BEGIN
            PLSQL_EXAMPLE.PROC_IN_INOUT(:test_num, :is_odd);
        END;
  });
  # The value of $test_num is _copied_ here
  $csr->bind_param(":test_num", $test_num);
  $csr->bind_param_inout(":is_odd", \$is_odd, 1);
  # The execute will automagically update the value of $is_odd
  $csr->execute;
  print "$test_num is ", ($is_odd) ? "odd - ok" : "even - error!", "\n";
  # Example 4
  #
  # What about the return value of a PLSQL function? Well treat it the same
  # as you would a call to a function from SQL*Plus. We add a placeholder
  # for the return value and bind it with a call to bind_param_inout so
  # we can access it's value after execute.
  my $whoami = "";
  $csr = $db->prepare(q{
        BEGIN
            :whoami := PLSQL_EXAMPLE.FUNC_NP;
        END;
  });
  $csr->bind_param_inout(":whoami", \$whoami, 20);
  $csr->execute;
  print "Your database user name is $whoami\n";
  $db->disconnect;

You can find more examples in the t/plsql.t file in the DBD::Oracle source directory.


Private database handle functions

These functions are called through the method func() which is described in the DBI documentation.

plsql_errstr

This function returns a string which describes the errors from the most recent PL/SQL function, procedure, package, or package body compile in a format similar to the output of the SQL*Plus command 'show errors'.

The function returns undef if the error string could not be retrieved due to a database error. Look in $dbh->errstr for the cause of the failure.

If there are no compile errors, an empty string is returned.

Example:

    # Show the errors if CREATE PROCEDURE fails
    $dbh->{RaiseError} = 0;
    if ( $dbh->do( q{
        CREATE OR REPLACE PROCEDURE perl_dbd_oracle_test as
        BEGIN
            PROCEDURE filltab( stuff OUT TAB ); asdf
        END; } ) ) {} # Statement succeeded
    }
    elsif ( 6550 != $dbh->err ) { die $dbh->errstr; } # Utter failure
    my $msg = $dbh->func( 'plsql_errstr' );
    die $dbh->errstr if ! defined $msg;
    die $msg if $msg;

dbms_output_enable / dbms_output_put / dbms_output_get

These functions use the PL/SQL DBMS_OUTPUT package to store and retrieve text using the DBMS_OUTPUT buffer. Text stored in this buffer by dbms_output_put or any PL/SQL block can be retrieved by dbms_output_get or any PL/SQL block connected to the same database session.

Stored text is not available until after dbms_output_put or the PL/SQL block that saved it completes its execution. This means you CAN NOT use these functions to monitor long running PL/SQL procedures.

Example 1:

  # Enable DBMS_OUTPUT and set the buffer size
  $dbh->{RaiseError} = 1;
  $dbh->func( 1000000, 'dbms_output_enable' );
  # Put text in the buffer . . .
  $dbh->func( @text, 'dbms_output_put' );
  # . . . and retreive it later
  @text = $dbh->func( 'dbms_output_get' );

Example 2:

  $dbh->{RaiseError} = 1;
  $sth = $dbh->prepare(q{
    DECLARE tmp VARCHAR2(50);
    BEGIN
      SELECT SYSDATE INTO tmp FROM DUAL;
      dbms_output.put_line('The date is '||tmp);
    END;
  });
  $sth->execute;
  # retreive the string
  $date_string = $dbh->func( 'dbms_output_get' );
dbms_output_enable ( [ buffer_size ] )
This function calls DBMS_OUTPUT.ENABLE to enable calls to package DBMS_OUTPUT procedures GET, GET_LINE, PUT, and PUT_LINE. Calls to these procedures are ignored unless DBMS_OUTPUT.ENABLE is called first.

The buffer_size is the maximum amount of text that can be saved in the buffer and must be between 2000 and 1,000,000. If buffer_size is not given, the default is 20,000 bytes.

dbms_output_put ( [ @lines ] )
This function calls DBMS_OUTPUT.PUT_LINE to add lines to the buffer.

If all lines were saved successfully the function returns 1. Depending on the context, an empty list or undef is returned for failure.

If any line causes buffer_size to be exceeded, a buffer overflow error is raised and the function call fails. Some of the text might be in the buffer.

dbms_output_get
This function calls DBMS_OUTPUT.GET_LINE to retrieve lines of text from the buffer.

In an array context, all complete lines are removed from the buffer and returned as a list. If there are no complete lines, an empty list is returned.

In a scalar context, the first complete line is removed from the buffer and returned. If there are no complete lines, undef is returned.

Any text in the buffer after a call to DBMS_OUTPUT.GET_LINE or DBMS_OUTPUT.GET is discarded by the next call to DBMS_OUTPUT.PUT_LINE, DBMS_OUTPUT.PUT, or DBMS_OUTPUT.NEW_LINE.


Using DBD::Oracle with Oracle 8 - Features and Issues

DBD::Oracle version 0.55 onwards can be built to use either the Oracle 7 or Oracle 8 OCI (Oracle Call Interface) API functions. The new Oracle 8 API is used by default and offers several advantages, including support for LOB types and cursor binding. Here's a quote from the Oracle OCI documentation:

  The Oracle8 OCI has several enhancements to improve application
  performance and scalability. Application performance has been improved
  by reducing the number of client to server round trips required and
  scalability improvements have been facilitated by reducing the amount
  of state information that needs to be retained on the server side.

Prepare postponed till execute

The DBD::Oracle module will avoid an explicit 'describe' operation prior to the execution of the statement unless the application requests information about the results (such as $sth->{NAME}). This reduces communication with the server and increases performance. However, it also means that SQL errors are not detected until execute() is called (instead of prepare() as now).

Handling LOBs

When fetching LOBs, they are treated just like LONGs and are subject to $sth->{LongReadLen} and $sth->{LongTruncOk}. Note that with OCI 7 DBD::Oracle pre-allocates the whole buffer (LongReadLen) before constructing the returned column. With OCI 8 it grows the buffer to the amount needed for the largest LOB to be fetched so far.

When inserting or updating LOBs some major magic has to be performed behind the scenes to make it transparent. Basically the driver has to refetch the newly inserted 'LOB Locators' before being able to write to them. However, it works, and I've made it as fast as possible, just one extra server-round-trip per insert or update after the first. For the time being, only single-row LOB updates are supported. Also passing LOBS to PL/SQL blocks doesn't work.

To insert or update a large LOB, DBD::Oracle has to know in advance that it is a LOB type. So you need to say:

  $sth->bind_param($field_num, $lob_value, { ora_type => ORA_CLOB });

The ORA_CLOB and ORA_BLOB constants can be imported using

  use DBD::Oracle qw(:ora_types);

or just use the corresponding integer values (112 and 113).

To make scripts work with both Oracle7 and Oracle8, the Oracle7 DBD::Oracle will treat the LOB ora_types as LONGs without error. So in any code you may have now that looks like

  $sth->bind_param($idx, $value, { ora_type => 8 });

you could change the 8 (LONG type) to ORA_CLOB or ORA_BLOB (112 or 113).

One further wrinkle: for inserts and updates of LOBs, DBD::Oracle has to be able to tell which parameters relate to which table fields. In all cases where it can possibly work it out for itself, it does, however, if there are multiple LOB fields of the same type in the table then you need to tell it which field each LOB param relates to:

  $sth->bind_param($idx, $value, { ora_type=>ORA_CLOB, ora_field=>'foo' });

Binding Cursors

Cursors can now be returned from PL/SQL blocks. Either from stored procedure OUT parameters or from direct OPEN statements, as show below:

  use DBI;
  use DBD::Oracle qw(:ora_types);
  $dbh = DBI->connect(...);
  $sth1 = $dbh->prepare(q{
      BEGIN OPEN :cursor FOR
          SELECT table_name, tablespace_name
          FROM user_tables WHERE tablespace_name = :space
      END;
  });
  $sth1->bind_param(":space", "USERS");
  my $sth2;
  $sth1->bind_param_inout(":cursor", \$sth2, 0, { ora_type => ORA_RSET } );
  $sth1->execute();
  # $sth2 is now a valid DBI statement handle for the cursor
  while ( @row = $sth2->fetchrow_array ) { ... }

The only special requirement is the use of bind_param_inout() with an attribute hash parameter that specifies ora_type as ORA_RSET. If you don't do that you'll get an error from the execute() like: ``ORA-06550: line X, column Y: PLS-00306: wrong number or types of arguments in call to ...''.


Oracle Related Links

Oracle on Linux

  http://www.datamgmt.com/maillist.html
  http://www.eGroups.com/list/oracle-on-linux
  http://www.wmd.de/wmd/staff/pauck/misc/oracle_on_linux.html
  ftp://oracle-ftp.oracle.com/server/patch_sets/LINUX

Free Oracle Tools and Links

  ora_explain supplied and installed with DBD::Oracle.
  http://vonnieda.org/oracletool/

Commercial Oracle Tools and Links

Assorted tools and references for general information. No recommendation implied.

  http://www.platinum.com/products/oracle.htm
  http://www.SoftTreeTech.com
  http://www.databasegroup.com

Also PL/Vision from RevealNet and Steven Feuerstein, and ``Q'' from Savant Corporation.


SEE ALSO

the DBI manpage


AUTHOR

DBD::Oracle by Tim Bunce. DBI by Tim Bunce.


COPYRIGHT

The DBD::Oracle module is Copyright (c) 1995,1996,1997,1998,1999 Tim Bunce. England. The DBD::Oracle module is free software; you can redistribute it and/or modify it under the same terms as Perl itself with the exception that it cannot be placed on a CD-ROM or similar media for commercial distribution without the prior approval of the author.


ACKNOWLEDGEMENTS

A great many people have helped me over the years. Far too many to name, but I thank them all.

See also ACKNOWLEDGEMENTS in the DBI manpage.

 DBD::Oracle - Oracle database driver for the DBI module