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JCB FAQ

General
Installation and configuration
Performance
Integration
Examples
Common issues
General
  • Which Java virtual machine should I use with JChem?

JChem requires Oracle Java Runtime Environment (JRE) 17 JRE Standard Edition or better. Equivalent JREs from other vendors may work, but not recommended. For maximum performance we recommend to use the latest stable release from Oracle.

  • I get out of memory error.

Java applications in general:

In the case of most Java Virtual Machines, the default setting of maximum heap size is 64MB. One can increase the maximum heap size of applications running under Oracle's environment by setting the -Xmx parameter. General example for allowing 128 MBytes for an application:

java -Xmx128m my.Application

JChem applications:

In the case of the JChem application startup files (Windows Batch Files and Unix Shell Scripts) an application-specific value is specified in the startup file, which can be easily edited. Please click here for further information.

Web applications:

If your problem occurs in Tomcat, please see the Tomcat configuration page.

If you use a different servlet server, then please consult the documentation of the software for details.

When using a MySQL database, an OutOfMemory Error may occur during a JChem table export of millions of structures. The MySQL database driver causes the problem, which fetches the data set in one batch.

We recommend you use the fetchSize option in the MySQL driver URL. See the example in the FAQ.

Please also see the "Memory" section of hardware requirements for more information.

  • I get a warning "Table could not fit into structure cache (out of memory)." .

This indicates that the table could not be loaded into the structure cache due to lack of sufficient memory. There should be sufficient memory for the Java Virtual Machine (JVM) to load the structural and fingerprint information of all structure tables.

Please see the section describing how to allocate the memory need for your structure tables.

The out of memory section describes how to allocate more memory for the JVM.

  • Can I use JChem Base in cloud environment?


    Yes, you can install it - for example - on an EC2 instance in Amazon and let it work with relational databases available anywhere, in the cloud or out of the cloud.
Installation and configuration

  • How to upgrade to a new JChem version?
    These are the steps that you should follow at upgrading:

    1. Download the latest JChem installation package

    2. Make sure no JChem applications are running

    3. Replace your old JChem directory with the contents of the new package. (delete/move the old directory and extract the package to the same location)

    4. Run the JChemManager (jcman) GUI, or execute the following command to update in text mode:

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       jcman u

    5. The application will automatically prompt you for the upgrades. Some of these changes are quick, however the regeneration of the tables can take for a while. The time requirement for table regeneration is comparable to the time of importing the same number of structures.

    6. If you are using JChem from other (standalone or web) applications, make sure you also update the .jar files used by them. These jar files are located under the jchem\lib directory in the unpacked package. You should also restart these applications, so they can load the new code from the updated .jar files

      For example if you are running a JSP application in Tomcat:

      • Stop Tomcat
      • Update the .jar files in Tomcat's lib directory.
      • Start Tomcat
  • JCMAN GUI does not work via X between Linux (server) and Windows (client)
    ​
    It is possible that JCMAN GUI does not work on Linux server with Windows client via X sever in some cases. Opening your ssh connection with -Y option may solve the problem.

    Related forum topic: https://forum.chemaxon.com/viewtopic.php?p=15322#15322

  • **How should I set the "JDBC driver" and "URL of database" fields for starting JChemManager? **

    One can find simple examples of JDBC URL and driver strings in the tables below.

    (For more complex cases please see the documentation of the JDBC driver.)

Notes:

  • ODBC connection is only tested and supported for Microsoft Access. For other databases the native JDBC drivers should be used.
  • For Oracle only the "thin" driver is tested and recommended ("oci" connection is not supported).

Supported databases:

Oracle
Driver oracle.jdbc.OracleDriver
URL format jdbc:oracle:thin:@::
URL example jdbc:oracle:thin:@localhost:1521:mydb
Supported versions 19c, 21c, 23ai
Continually tested versions Oracle 19c Standard Edition,
Oracle 21c Standard Edition
Oracle 23ai Standard Edition
More information
MySQL
Amazon Aurora MySQL
Driver org.mariadb.jdbc.Driver
(up to version 17.3.27: com.mysql.jdbc.Driver)
URL format
URL format for Aurora		 jdbc:mysql://:/[?options]
in the case of mariadb option useMysqlMetadata=true must be added
jdbc:mysql:aurora://:/[?options]
URL example jdbc:mysql://localhost:3306/mydb?useCursorFetch=true&defaultFetchSize=1000
jdbc:mariadb://localhost:3306/mydb?useMysqlMetadata=true
Supported versions MySQL 5.7. 8.0
Continually tested versions MySQL 8.0
More information
IBM DB2
Driver com.ibm.db2.jcc.DB2Driver
Supported versions IBM DB2 10.5, 11.1, 11.5
More information
MS SQL Server
Driver com.microsoft.sqlserver.jdbc.SQLServerDriver
URL format jdbc:sqlserver://:<;databaseName=database>[;options]
URL Example jdbc:sqlserver://localhost:1433;databaseName=mydb;selectMethod=cursor Note : schema name cannot be specified; jchem uses the default schema: 'dbo'
Supported versions MS SQL Server 2012, 2014, 2016, 2017, 2019
Continually tested versions MS SQL Server 2012
More information
HSQLDB / HXSQL
Driver org.hsqldb.jdbcDriver
URL format jdbc:hsqldb:hsql://[host]/[database]
URL Example jdbc:hsqldb:hsql://localhost/
Supported versions HSQLDB 2.4, 2.4.1, 2.5, 2.5.1, 2.6
More information
MS Access via ODBC
Driver sun.jdbc.odbc.JdbcOdbcDriver
URL format jdbc:odbc:[odbc data source][;options]
URL example jdbc:odbc:mydatasource
Supported versions all via odbc
Derby
Driver org.apache.derby.jdbc.EmbeddedDriver
URL format jdbc:derby:[subprotocol]:[database with path][;create=true][;options]
URL example jdbc:derby:/c:/databases/mydb;create=true
Supported versions versions embedded with Java
Continually tested versions versions embedded with Java 17
More information
PostgreSQL Amazon Aurora PostgreSQL
Driver org.postgresql.Driver
URL format jdbc:postgresql://:/
URL example jdbc:postgresql://localhost:5432/mydb
Supported versions PostgreSQL 13, 14, 15, 16, 17
Continually tested versions PostgreSQL 17
More information
InterBase
Driver interbase.interclient.Driver
URL format jdbc:interbase:[path to interbase data file (.gdb file)]
URL example jdbc:interbase://localhost/c:/interbase/interbasedb.gdb
Supported versions InterBase 2017, 2020
More information

  • Why do I get SQLException or other error when I use JChemManager?

The most probable causes:

    • Incorrect URL to the database (it may occur during login)
    • Inappropriate username / password (it may occur during login)
    • Faulty JDBC or ODBC driver. Try a different one.

  • I get exception when I start JChemManager using Oracle's JDBC thin driver.

Make sure that the URL is appropriate (e.g: jdbc:oracle:thin:@myhost:1521:mySID). Check if all needed services run (the listener service is necessary).


  • JChem Manager and chemaxon.jchem.db.Importer fails to import date formats into PostgreSQL tables which otherwise work with psql or other non-JDBC-based clients

If this is a date or time stamp format which works using psql or other non-JDBC-based database clients, you have likely run into this PostgreSQL JDBC issue:

The work-around is to to append stringtype=unspecified to the connection.jdbcUrl:

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connection.jdbcUrl=jdbc\:postgresql\://localhost\:5432/jcbtest?stringtype=unspecified

  • ##### Integration


    • How can I use the JChem API from my favorite programing language (C++, C#, .NET, Python, Javascript, Perl)?

For users of the .NET API, the JChem API can be integrated into .NET applications by the .NET Packages. Other web service compatible languages (including C++ and C#) can use JChem Web Services.


  • How can I use the JChem tools as a web service?

Many of the JChem tools are available as web services. See the JChem Web Services Server for more information

  • ##### Examples


    • Where can I find examples for using JChem?

      • A JSP (Java Server Pages) and ASP examples can be found in the examples directory. Please see {{/examples/index.html}} for a description.

    • How should I set the connection string in the case of ASP or other ADO capable environment?

If you would like to call SQL statements using ADO, you may choose between ODBC and OLEDB connections. (ADO can not contact to the databases through JDBC drivers.)

  • Example for an ODBC connection
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    var adoConnectionString=
    "DSN="+MyDSN+";"+
    "UID="+username+";"+
    "PWD="+password;
  • Example for an OLEDB connection to Oracle
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    var adoConnectionString=
    "Provider=MSDAORA.1;"+
    "Data Source="+myServiceName+";"+
    "User ID="+username+";"+
    "Password="+password;

(The above examples use the JavaScript syntax)

In the case of Oracle, if an error occurs, please see HOWTO: Troubleshoot an ASP-to-Oracle Connectivity Problem


    • Copy/paste doesn't work with a certain Look and Feel. 
      1
      Keyboard shortcuts for Copy/Paste/Cut functions may vary by Look and Feel. For example in the case of Windows Look and Feel these are `CTRL+C,CTRL+V`, and `CTRL+X`, respectively. In the case of Motif LF the shortcuts for the same commands are: `CTRL+INS,SHIFT+INS`, and `SHIFT+DEL`.

  • ##### Common issues

    • *I get the following exception using MySQL: *com.mysql.jdbc.PacketTooBigException: Packet for query is too large **

Please increase the value of the "max_allowed_packet" variable for MySQL. The following line should be added to the configuration file "my.ini" under the [mysqld] section :

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 max_allowed_packet = 100M

  • I get the following error message : " The structure table contains obsolete data. Please regenerate the table. " What does it mean ?

    Sometimes there are some changes in the data structure of JChem, which are incompatible with earlier versions. To obtain correct search result, the regeneration of the old structure tables is necessary. For more information and instructions please see the administration guide.


  • In DB2 databases, row length of JChem structure tables has been increased

    Please, be aware of the increased (by about 1K) row lengths of the JChem structure tables from JChem 6.1.2. It's possible that the new row length will reach the maximum row length allowed in your database. In this case the extended row size support must be enabled or the page size of the tablespace must be increased manually.

  • How to check for duplicates in duplicate filtered tables

    Because of a bug - fixed in JChem version 17.29.0 - duplicates could have been inserted in tables with duplicate filtering set on if there were too many structures with the same hash code already in the database. Starting from JChem version 18.1.0, a command line tool * duplicatecheck * is provided for finding the duplicates in a JChem table. This tool is available in the * bin * folder of JChem. For detailed help please run:

    duplicatecheck -help