Information Management IBM Informix Dynamic Server © 2008 IBM Corporation KC Informix Users Group 10 Cheetah 2 Features Presented By: Sanjit Chakraborty

Information Management

IBM Informix Dynamic Server © 2008 IBM Corporation

KC Informix Users Group 10 Cheetah 2 Features

Presented By: Sanjit Chakraborty / Jeff LaubeDate: Jan 22, 2009



IDS 11.50 ( Cheetah 2)

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Agenda

1. Enhanced Configuration Options During Installation2. Automatic Statistics Updating3. Control External Directives for a Session4. Automatic Statistics & Distributions with Create Index5. Enhanced Startup script customization6. Visual Explain7. BIGINT/BIGSERIAL8. Secure Socket Layer (SSL)9. Savepoints10. LIMITNUMSESSIONS



KC Informix Users Group

Feature 1: Enhanced Configuration Options During Installation




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Enhanced Configuration Options During Installation

Instance Configuration Wizard

Automatically creates and custom onconfig file for future use

The onconfig file generates during create demonstration database server with custom setup

GUI and Console installation wizard both supports

Windows limitation –– Only available with a custom setup in GUI mode

– Not available with silent installation

Parameters value decides depending on hardware and database system needs

Configuration file generated with Standard setting for any error encountered during using wizard




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Input for Configuration File

Installation Directory Database Server Name Server Number Rootpath Rootsize No. of central processing units (CPUs) Memory: System RAM dedicated to the IDS server (in MB) No. of online transaction clients No. of decision support clients




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Updated Configuration Parameters

ROOTPATH ROOTSIZE MSGPATH DBSERVERNAME DBSERVERALIASES SERVERNUM ALARMPROGRAM DRLOSTFOUND BAR_ACT_LOG BAR_DEBUG_LOG SYSALARMPROGRAM DUMPDIR JVPJAVAHOME JVPHOME JVPPROPFILE JVPLOGFILE JVPCLASSPATH BUFFERPOOL VPCLASS




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Files Generated Customized Onconfig file

– <INFRMIXDIR>/etc

Onconfig file

– onconfig.<server name>

Updated onconfig parameters will be added at bottom of the file

Environment Setup Files

– <INFRMIXDIR>/demo/server

– profile_settings (ksh)– Profile_settings.csh




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Enhanced Configuration Options During InstallationInstance Configuration Wizard UNIX install (either Typical or Custom)

Do you want to create an IDS demonstration database server instance?

[X] 1 - Yes[ ] 2 - No

Demonstration Database Instance Configuration

[ ] 1 - Use my own configuration file.[ ] 2 - Use the default configuration file.[X] 3 - Customize the default configuration file to suit your needs and hardware.

Specify your server configuration parameters (Server Number should be in the range of 0 to 255).

Server Name [demo_on] ids1150

Server Number [0] 50

ROOTPATH [/usr2/products/11.50.UC2/demo/server/online_root] /chunks/1152/chunk1

ROOTSIZE (MB) [760] 204800

Press 1 for Next, 2 for Previous, 3 to Cancel or 4 to Redisplay [1]

Configuration Setup

Modify any values if you want to customize database server configuration settings.

Processors to use [1] 1

Memory to use (MB) [512] 128

Online Transaction Clients (applications that frequently update databases with multiuser input) [1] 1000

Decision Support Clients (applications for querying databases to gather reporting information) [1] 25




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Enhanced Configuration Options During InstallationInstance Configuration Wizard

Installation log after configuration parameters set:

Installing IBM Informix Dynamic Server Version 11.50. Please wait...

Creating demonstration database server instance ...

Creating demonstration database server instance ... - Creating demonstration database server onconfig file at

/usr2/products/11.50.UC2/etc/onconfig.ids1150

Creating demonstration database server instance ... - Demonstration database server instance initialized successfully .

Please read the information below.

The IBM Informix Dynamic Server demonstration database server has been created.Check the log file to determine if it was successfully initialized: /usr2/products/11.50.UC2/demo/server/online.log.

(Note: the above log is the verbose output to screen, it is not logged to a physical file)




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Enhanced Configuration Options During InstallationInstance Configuration Wizard Windows install




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Feature 2: Automatic Statistics UpdatingAutomatic Statistics Updating (AUS)




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Why Auto Update Statistics (AUS)? Users must update statistics and distributions manually to

help optimizer make correct decisions to run query efficiently– Many of us do not realize this and encounter poor

performance

When to run Update Statistics?

What statistics and distributions need to be updated?– Not easy to understand

– Change periodically

– Differ for each system

AUS provides ability to automate the maintenance of optimizer statistics




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AUS Implementation

A set of procedures which will be invoked by the database scheduler to automate update statistics– Installed as part of the server– Users can write SQL statements to manipulate the

AUS configuration

Open Admin Tool (OAT) graphical interface allows easier control of the different AUS policies– Open source download available from iiug.org and

IBM websites

– Display AUS information in easy to read format

– Simple point and click interface




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AUS Implementation - Database Tasks Tasks in ph_task table Auto Update Statistics Evaluation

– Analyzes all the tables in all logged databases

– Locates tables which require new or updated optimizer statistics

– Builds the update statistics commands

– Inserts the commands into the table aus_cmd_list

Auto Update Statistics Refresh– Executes the update statistics commands from

aus_cmd_list table in a priority order within a specified time

– After the command completes, it is moved to the aus_cmd_comp table




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Configuration Parameters – PH_THRESHOLD Table

ph_threshold Table Parameter

Default Value

Description

AUS_AGE 30 days How old the statistics or distributions can be before they will be updated; even if there are no changes.

AUS_CHANGE 10 If the table has changed by more than this percentage then the statistics and distributions will be updated.

AUS_AUTO_RULES 1 Turning this on will ensure statistics and distributions are updated to a Informix minimum suggested guidelines. If the current statistics or distributions exceed the minimum suggested guidelines then the current setting will be used.

AUS_SMALL_TABLES 100 Tables containing less than this number of rows will always have their statistics rebuilt.

AUS_PDQ 10 Auto Update statistics executes with this PDQ priority.

Use OAT AUS configuration page or update sysadmin:ph_threshold tomodify these parameters




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Scheduling Information

Since AUS is a resource intensive operation, a specific run window can be defined. The run window definition includes start time, the end time and the days of the week to run the job.

Can be configured from the Open Admin tool.

Implemented by setting the start and end times of the AUS refresh (Auto Update Statistics Refresh) task in ph_task table in sysadmin.

Default runtime window is 1:00 AM – 5:00 AM daily.

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Feature 3: Automatic Statistics & distributions With Create Index




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Indexes and Statistics/Distributions

Without statistics or distributions the index will not be considered by the

optimizer

Common Mistake

– Create an index and see no improvement in select performance

We need to run UPDATE STATISTICS LOW at a minimum for newly created indexes to be considered for query access plans.

Why can’t this be done automatically when new indexes are created?




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Create Index Distributions & Statistics

Implicit or explicit CREATE INDEX automatically creates statistics & distribution for the leading column of an index

– UPDATE STATISTICS LOW Statistics

– UPDATE STATISTICS HIGH Distribution

SET EXPLAIN Output for CREATE INDEX statement: CREATE INDEX idx1 on tab1(col1_int)

Index: idx1 on informix.tab1STATISTICS CREATED AUTOMATICALLY:Column Distribution for: informix.tab1.col1_intMode: HIGHNumber of Bins: 207 Bin size: 4800.0Sort data: 0.9 MBCompleted building distribution in: 0 minutes 1 seconds

Enabled always -- cannot turn off




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Limitations to Create Index Distributions Index distributions are NOT created when --

– If the lead of the index is a UDT (builtin or non-builtin)

– Index is a functional index

– Index is a VII index

– Number of rows in table is < 2

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Feature 4: Control External Directives for a SessionControl External Directives for a Session




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External Directives (Previous references)

Query performance problems and you cannot change it because

You don’t own the application or a 3rd party application

You don't have the source code access or the developer is unavailable

The application is heavily used and can't be switched off without schedule a downtime

Update statistics or change OPTCOMPIND

doesn't affect




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External Directives (Previous references)

External optimizer directives are useful when it is not feasible rewrite a query for a short-term solution to a problem

Enabling external directives

Environment Variable: IFX_EXTDIRECTIVES

Configuration parameter: EXT_DIRECTIVES

SQL Syntax:

SAVE EXTERNAL DIRECTIVES <directive name> [ACTIVE | INACTIVE | TEST ONLY] FOR <query>

Directives saved in sysdirectives catalog




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Example: External Directive

Schema for table itemscreate table items

(

item_num smallint,

order_num integer,

stock_num smallint not null ,

manu_code char(3) not null ,

quantity smallint,

total_price money(8,2)

);

create index items_idx1 on items (item_num, manu_code);

Query runs from an application which used the items_idx1 index path SELECT item_num, manu_code

FROM items

WHERE manu_code = "ANZ"




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Example: External Directive (cont.)

Some reason query is running slow because of sequential scan instead follow the index path

Update statistics is not helpful

Only way query can ran faster, using INDEX directive

SELECT {+INDEX (items item_idx1)}

item_num, manu_code

FROM items


Without changing the application code force optimizer to chose the index path

Solution is use external directive




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Example: External Directive (cont.)

Save and Active the query as external directiveSAVE EXTERNAL DIRECTIVES --+INDEX(items item_idx1)

ACTIVE FORSELECT item_num, manu_code

FROM items


If external directive enabled, query should follow the index pathEnvironment Variable: IFX_EXTDIRECTIVES

Configuration parameter: EXT_DIRECTIVES




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Session Level External DirectivesOverview

New EXTDIRECTIVES session environment option of the SET ENVIRONMENT statement

Overwrites the EXT_DIRECTIVES configuration parameter

Controls whether external directives are enabled, disabled or have default behavior during a session

Default behavior specified in the EXT_DIRECTIVES ONCONFIG parameter and client-side environment variable IFX_EXTDIRECTIVES




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Control External Directives for a Session

Syntax

SET ENVIRONMENT EXTDIRECTIVES ‘[DEFAULT | off | on]’; orSET ENVIRONMENT EXTDIRECTIVES ‘[DEFAULT | 0 | 1]’;

Example

* Disable external directives within a session SET ENVIRONMENT EXTDIRECTIVES ‘off’;

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Feature 5: Enhanced Startup script Enhanced Startup script customization customization




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New oninit option: -w Use to customize startup scripts and automate

startup for the oninit utility.

The -w option forces the server to wait until it successfully initializes before returning a shell prompt.

The -w option provides a return code so that you can check if the IDS started without incident

return 0 when successreturn 1 when initialization fails or

configurable timeout achieved

In case of failure online.log updated appropriately




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oninit -w <delay>

Configurable timeout period during server initializes

oninit –w <delay in seconds>

If fails return 1 with a message in online.log:Warning: wait time expired

Default timeout: 600 sec

Return code 1- Not necessary server crash or failure




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Notes

In a high-availability environment, you can only use the oninit -w command on primary servers; it is not valid on secondary servers

Returns success when sysmaster, sysutils, sysuser and sysadmin are successfully created

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Feature 6: Visual Explain




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Visual Explain

A new user defined function (C-UDR) EXPLAIN_SQL was implemented in IDS11.50.

The new UDR EXPLAIN_SQL can be used to obtain a query explain output in XML format.

IBM Data Studio can interpret the XML formatted explain file and show the query plan graphically to the user.




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EXPLAIN_SQL UDR is mainly implemented to allow common tooling such as the new IBM Data Studio to be able to get XML explain output through the function and show users the graphical query plans.

If user wants to obtain the XML explain output and use their own graphic tool to see the query plan, the UDR should be ran by JDBC or JCC program.

Visual Explain




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Example of JDBC program running EXPLAIN_SQL

CallableStatement cstmt2 = conn.prepareCall("{call informix.explain_sql(?, ?, ?, ?, ?, ?, ?)}");

/* set up the parameters */cstmt2.registerOutParameter( 1, Types.INTEGER );cstmt2.registerOutParameter( 2, Types.INTEGER );cstmt2.setString(3,null);cstmt2.setNull( 5, Types.BLOB ); // Filtercstmt2.registerOutParameter( 6, Types.BLOB ); // XML_OUTPUTcstmt2.registerOutParameter( 7, Types.BLOB ); // XML_MESSAGE

file = new File("./xmlins");fin = new FileInputStream(file); byte[] buffer = new byte[8000];

IfxLobDescriptor loDesc = new IfxLobDescriptor(conn);IfxLocator loPtr = new IfxLocator();IfxSmartBlob smb = new IfxSmartBlob(conn);int loFd = smb.IfxLoCreate(loDesc, smb.LO_RDWR, loPtr);

n = fin.read(buffer);if (n > 0) n = smb.IfxLoWrite(loFd, buffer); smb.IfxLoClose(loFd);Blob blb = new IfxBblob(loPtr);cstmt2.setBlob(4, blb); // set the blob column

Visual Explain




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Example of JDBC program running EXPLAIN_SQL … continued

ResultSet rs = cstmt2.executeQuery();

int outmajver = cstmt2.getInt(1);int outminver = cstmt2.getInt(2);

/* read the xml explain output if there is any */while (rs.next()) { byte[] buf = new byte[80000]; b = (IfxBblob) rs.getBlob(1);

if (b != null {

IfxLocator loptr = b.getLocator();

IfxSmartBlob smbl = new IfxSmartBlob(conn);

int lofd = smbl.IfxLoOpen(loptr, smbl.LO_RDONLY);

outfile = new File("./out.xml");

fout = new FileOutputStream(outfile);

int size = smbl.IfxLoRead(lofd, fout, 80000);

smbl.IfxLoClose(lofd);

smbl.IfxLoRelease(loptr); } }

Visual Explain




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Example of JDBC program running EXPLAIN_SQL … continued

/* get blob out parameters */ outmsg_b = (IfxBblob)cstmt2.getBlob(7); if (outmsg_b == null) System.out.println("outmsg_b is null"); else {

IfxLocator xml_msg_loptr = outmsg_b.getLocator();

IfxSmartBlob xml_msg_smbl = new IfxSmartBlob(conn);

int msg_out_lofd = xml_msg_smbl.IfxLoOpen(xml_msg_loptr,

xml_msg_smbl.LO_RDONLY);

msg_out_outfile = new File("./xml_msg.xml");

msg_out_fout = new FileOutputStream(msg_out_outfile);

int xml_msg_size = xml_msg_smbl.IfxLoRead(msg_out_lofd,

msg_out_fout, 80000);

xml_msg_smbl.IfxLoClose(msg_out_lofd);

xml_msg_smbl.IfxLoRelease(xml_msg_loptr); }

Visual Explain




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Sample XML explain output

<?xml version="1.0" encoding="UTF-8"?><explain dbplatform="IDS" dbversion="11.11" timestamp="11-14-2007 11:50:29">

<plans><source>

<query>select * from chartab where c1 = 2 ;</query></source><dataview id="v0" type="label">

<dataseq dataid="0" /></dataview>

...<diagram id="g0" name="Query" structure="tree">

<node id="n0" type="060f002b" labelviewid="l0"><descriptorlink descriptorid="d0" />...<node id="n3" type="0212003a" labelviewid="l3">

<descriptorlink descriptorid="d3" /></node>

</node></diagram><descriptor id="d0" name="Query" type="ids.query">

<datatitle nametitle="NAME">VALUE</datatitle></descriptor> ...

</plans></explain>

Visual Explain




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Sample visual explain in Data studio

Visual Explain




Feature 7: BIGINT / BIGSERIAL




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BIGINT / BIGSERIAL Overview:

New ANSI standard SQL data types BIGINT and BIGSERIAL were introduced in IDS.

Aims to provide a better performance alternative to INT8 and SERIAL8 data types. However, IDS will continue its support of INT8 and SERIAL8 data types in existing customer applications.




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BIGINT / BIGSERIAL Description INT8 and SERIAL8 data types which are internally implemented as a

10-byte structure, ifx_int8_t. INT8 and SERIAL8 take up to 10 byte of storage in IDS.

This feature will implement BIGINT and BIGSERIAL data types using

native 8-byte integers. It will take 8-byte to store these data types.

Like INT8, BIGINT will store numbers range from 9,223,372,036,854,775,807 to 9,223,372,036,854,775,807 [(2^63-1) to 2^63-1].

The number –9,223,372,036,854,775,808 is a reserved for a NULL value and cannot be used.




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BIGINT / BIGSERIAL Description Like SERIAL8, BIGSERIAL will store numbers range from 1

to 9,223,372,036,854,775,807 [or 1 to 2^63-1]. Compare to INT8, BIGINT requires less storage space and

more important, should offer better performance in general because all arithmetic operations will be done using the native 8-byte integer instead of dealing with the 10-byte ifx_int8_t structure.

BIGINT and BIGSERIAL will be reserved keywords.

A table can have only one SERIAL column, and either one SERIAL8 column or one BIGSERIAL column.




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BIGINT / BIGSERIAL Description BIGINT and BIGSERIAL uses native 8-byte data type of the

OS. On 32-bit platforms it is ‘long long’. Under certain compiler options the ‘long long’ is not supported. During compilations of customer application if they detect error they can remove the Compiler option that causes not define ‘long long’. The alternative to this compile with –DNOBIGINT, by doing this customer may not be able to use this feature fully in their applications.

The new SQL data types will be classified as Exact Numeric Types under Built-in Data Types and will be applicable to all DDL/DML statements wherever built-in data types are currently used.




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BIGINT / BIGSERIAL Description

The BIGINT and BIGSERIAL SQL data types is supported in the following products– IDS and its Utilities

– ESQL/C

– ODBC

– JDBC

– Common Clients and derivatives




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BIGINT / BIGSERIAL Example CREATE TABLE T1 (C1 BIGSERIAL(12345), C2 BIGINT);

CREATE UNIQUE INDEX IX1 ON T1(C2);

INSERT INTO T1 VALUES (0, 1234567);

CREATE TABLE CT1 ( A BIGINT , B BIGSERIAL) FRAGMENT BY EXPRESSION

A <= 1000000000 IN DBSPACE2,A > 1000000000 AND A <= 29990000000 IN DBSPACE3,A > 29990000000 AND A <= 999999999999999 IN DBSPACE1;




Feature 8: Secure Socket Layer (SSL)




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Secure Socket Layer Communication protocol that provides privacy and integrity for data

communication over the network

Uses encryption to provide end-to-end secure connection

At present, IDS supports encrypted communication only with SQLI clients (using Encryption Communication Support Module)

With SSL, encrypted communication will be possible with DRDA clients too




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Digital Certificates, Certificate Authority (CA) and Keystores

Digital Certificates are electronic ID cards issued by trusted parties know as Certificate Authority (e.g. VeriSign)

SSL feature in IDS uses digital certificates to exchange keys for encryption and server authentication

Digital certificates are stored in key database (also known as keystore)

IBM’s Global Security Kit bundled with IDS server and client provides an iKeyman utility that can be used to create keystores and manage digital certificates




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Digital Certificates cont…

Both client and server must have keystore for housing digital certificates

Server side keystore will store digital certificate issued (or signed) by Certificate Authority such as VeriSign

Client side keystore will store digital certificate of Certificate Authority (also called root certificate) that issued the server digital certificate




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Setting up SSL - SQLHOSTS New communication protocol

– drsocssl protocol for supporting SSL communication with DRDA clients

– onsocssl/olsocssl protocol for supporting SSL communication with SQLI clients. SSL will also be supported with server to server communication (ISTAR, HDR, ER, SDS/RSS)

Example– lenexa_on onsoctcp pinchy lenexa_serv

– menlo_on onsocssl pinchy menlo_serv

– portland_on drsocssl pinchy portland_serv




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Setting up SSL - ONCONFIG

New parameters– SSL_KEYSTORE_LABEL – Specifies label of server digital certificate in keystore. If not

configured, the server will use the default label in keystore for SSL communication

e.g. SSL_KEYSTORE_LABEL ids_label

Changes to existing parameters– NETTYPE – Describes connection parameters such as number of poll threads, max

connections and class of virtual process for poll threads for connection protocols

NETTYPE protocol, poll threads, connections, VP class

Specify the protocol as iiippp

where: iii=[ipc|ipc|soc|tli]

ppp=[shm|str|tcp|spx|imc|ssl]

e.g. NETTYPE socssl, 3, 50, NET




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Setting up SSL - ONCONFIG

All SSL encryption/decryption operations are performed on encrypt VP. Encrypt VPs can be configured via VPCLASS parameter

e.g. VPCLASS encrypt, num=5

SSL and non-SSL connection protocols can be configured for a single instance using server aliases

e.g. DBSERVERNAME menlo_on

DBSERVERALIASES lenexa_on, portland_on

where menlo_on is onsocssl, lenexa_on is onsoctcp and

portland_on is drsocssl connection protocol




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Setting up SSL – Keystores and Digital certificates

IBM’s Global Security Kit (GSKit) will be installed as part of IDS and CSDK installations

GSKit contains iKeyman utility that can be used to create keystores and manage digital certificates needed for SSL communication

More information on iKeyman is available at:

http://w3-03.ibm.com/software/sales/saletool.nsf/resources/GSKITiKeyman/$file/GSK7c_SSL_Ikm_Guide.pdf




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The keystore for server is password protected. Password is stored encrypted in stash file (also created by iKeyman utility)

One keystore per server instance. It stores server’s digital certificate and root CA certificates of other servers its connecting to (as in ISTAR, HDR, ER, SDS/RSS)

Location and name of server keystore and its password stash file is predefined:

$INFORMIXDIR/ssl/<servername>.kdb

$INFORMIXDIR/ssl/<servername>.sth

The ownership/permissions of above files must be informix:informix/600

<servername> is value of DBSERVERNAME onconfig parameter




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Password is optional for client keystore.

Client keystore stores root CA certificates of all servers the client is connecting to. SQLI and DRDA clients can share same keystore

Location and name of client keystore and its password stash file can be configured via new configuration file:

– $INFORMIXDIR/etc/conssl.cfg

New client configuration parameters:

– SSL_KEYSTORE_FILE – Specifies fully qualified filename of client keystore

– SSL_KEYSTORE_STH – Specifies fully qualified filename of client stash file

If conssl.cfg does not exist or if any of above parameters are not configured, the keystore and stash file will default to:

$INFORMIXDIR/etc/client.kdb and $INFORMIXDIR/etc/client.sth




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Prerequisites for iKeyman utility– IBM JDK/JRE 1.3.1, 1.4.1 or higher with JCE PKS Security packages

Environment for iKeyman utility– export JAVA_HOME=<JDK/JRE installation>

– export PATH=$JAVA_HOME/jre/bin:$PATH

– export CLASSPATH=<GSKit installation>/classes/cfwk.zip:<GSKit installation>/classes/gsk7cls.jar:$JAVA_HOME/jre/lib/ext/ibmpkcs11.jar




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Sample commands for creating keystore and self-signed testcertificates* using iKeyman command line utility:

Server Keystore– gsk7cmd -keydb -create -db menlo_on.kdb -pw snoopy -type cms -stash

– gsk7cmd -cert -create -db menlo_on.kdb -pw snoopy -label ids_label -dn "CN=menlo.ibm.com,O=ibm,C=US" -size 1024 -default_cert yes

– gsk7cmd -cert -extract -db menlo_on.kdb -format ascii -label ids_label -pw snoopy -target ids_label.cert

where DBSERVERNAME is menlo_on SSL_KEYSTORE_LABEL is ids_label

Client Keystore– gsk7cmd -keydb -create -db client.kdb -pw snoopy -type cms -stash

– gsk7cmd -cert -add -db client.kdb -pw snoopy -label ids_label -file ids_label.cert -format ascii

*In production systems, digital certificates will be requested from Certificate Authority. Refer to iKeyman User Guide for more information on this.




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Recap of SSL setup

sqlhosts for client and server– onsocssl/drsocssl

onconfig for server– SSL_KEYSTORE_LABEL

– NETTYPE for socssl

– VPCLASS for encrypt VP

conssl.cfg for client– SSL_KEYSTORE_FILE

– SSL_KEYSTORE_STH

keystores and digital certificates for client and server

Initialize server and all communication between client and server or between servers on onsocssl/drsocssl port will be encrypted using SSL protocol




Feature 9: Savepoints




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Savepoint Description New SQL statements and options offer a mechanism to undo

portions of an SQL transaction

A user can arbitrarily mark points within one SQL transaction, called a savepoint

If an error occurs during execution, it can rollback the database changes made between the time the savepoint was started and the time the savepoint rollback request is issued.




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Savepoint: new SQL Establish a savepoint

<savepoint statement> ::= SAVEPOINT <savepoint_name> [UNIQUE]

[ON ROLLBACK RETAIN CURSORS]

[ON ROLLBACK RETAIN LOCK]

Destroy a savepoint

<release savepoint statement> ::= RELEASE SAVEPOINT <savepoint name>




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Savepoint: Enhanced SQL Rollback to a savepoint

<rollback to savepoint statement> ::=ROLLBACK [WORK] TO SAVEPOINT [<savepoint name>]




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Savepoint Example

SAVEPOINT order_two;

order:

UPDATE goods_one SET count = count – order_quantity;UPDATE goods_two SET count = count – order_quantity;

# if any of the above two statements fail, rollback to savepoint order_two

ROLLBACK TO SAVEPOINT order_two;order_quantity -=20;goto order;

#if both update statements succeed, erase the savepoint order_twoRELEASE SAVEPOINT order_two;




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Savepoints and JDBC JDBC will support this feature implementing these standard

methods defined in java.sql.Connection interface.

Savepoint setSavepoint() throws SQLException;

Savepoint setSavepoint(String name) throws SQLException;

Void rollback(Savepoint savepoint) throws SQLException

Void releaseSavepoint(Savepoint savepoint) throws SQLException




Feature 10: LIMITNUMSESSIONS




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LIMITNUMSESSIONS New ONCONFIG parameter:

LIMITNUMSESSIONS max#sessions, print_warning

max#sessions = 0 to 2097152. The default is 0.print_warning = 0 (off) or 1 (on). The default is 0.

Defines the max number of sessions that you want connected to IDS.

Warning messages will be reported to the online.log as the max value is approached if print_warning is on.




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LIMITNUMSESSIONS Example ONCONFIG setting:

LIMITNUMSESSIONS 100,1

Because print_warning is on, an online.log message reports that the max number of sessions, 100, is being approached as the number of user sessions closes in on this limit

If user session 101 attempts to connect to the server, the error -25571 is reported to client and a message in the online.log reports that the maximum number of sessions has been reached and no new sessions can connect until the current number of connections falls below this limit




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LIMITNUMSESSIONS Additional Information

LIMITNUMSESSIONS is not intended to provide a means for enforcing user license agreements.

LIMITNUMSESSIONS will not affect informix or DBSA users.




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Documents

Information Management IBM Informix Dynamic Server © 2008 IBM Corporation KC Informix Users Group 10 Cheetah 2 Features Presented By: Sanjit Chakraborty