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Administering
In addition to administering the database server, you can tune performance, replicate data, and archive data.
System administration
These topics contain concepts, procedures, and reference information for database and database server administrators to use for managing and tuning HCL Informix® database servers.
Administrator's Guide
The Informix® Administrator's Guide provides the information required to administer HCL Informix.
Disk, memory, and process management
Virtual processors and threads
These topics describe virtual processors, explain how threads run within the virtual processors, and explain how the database server uses virtual processors and threads to improve performance.
Virtual processor classes
Each class of virtual processor is dedicated to processing certain types of threads.
User-defined classes of virtual processors
You can define special classes of virtual processors to run user-defined routines or to run a DataBlade® module.
User-defined virtual processors
User-defined classes of virtual processors protect the database server from ill-behaved user-defined routines.

Administering
In addition to administering the database server, you can tune performance, replicate data, and archive data.
- System administration
  These topics contain concepts, procedures, and reference information for database and database server administrators to use for managing and tuning HCL Informix® database servers.
  - List of utilities
    HCL Informix® includes utilities and applications that you can use to perform administrative tasks and capture information about configuration and performance.
  - Administrator's Guide
    The Informix® Administrator's Guide provides the information required to administer HCL Informix.
    - The database server
    - Disk, memory, and process management
      - Virtual processors and threads
        These topics describe virtual processors, explain how threads run within the virtual processors, and explain how the database server uses virtual processors and threads to improve performance.
        Virtual processors
        A virtual processor is a process that the operating system schedules for processing.
        How virtual processors service threads
        A virtual processor services multiple threads concurrently by switching between them.
        Virtual processor classes
        Each class of virtual processor is dedicated to processing certain types of threads.
        CPU virtual processors
        The CPU virtual processor runs all session threads (the threads that process requests from SQL client applications) and some internal threads.
        User-defined classes of virtual processors
        You can define special classes of virtual processors to run user-defined routines or to run a DataBlade® module.
        Determine the number of user-defined virtual processors needed
        You can specify as many user-defined virtual processors as your operating system allows.
        User-defined virtual processors
        User-defined classes of virtual processors protect the database server from ill-behaved user-defined routines.
        Specify user-defined virtual processors
        The VPCLASS parameter with the vpclass option defines a user-defined VP class. You also can specify a nonyielding user-defined virtual processor.
        Assign a UDR to a user-defined virtual-processor class
        The SQL CREATE FUNCTION statement registers a user-defined routine.
        Add and drop user-defined virtual processors in online mode
        You can add or drop virtual processors in a user-defined class while the database server is online.
        Tenant virtual processor class
        Tenant virtual processor classes are specific to tenant databases. If you configure multitenancy for your Informix® instance, you can specify that session threads for tenant databases are run in tenant virtual processors instead of CPU virtual processors.
        Java™ virtual processors
        Java™ UDRs and Java applications run on specialized virtual processors, called Java virtual processors (JVPs).
        Disk I/O virtual processors
        The following classes of virtual processors perform disk I/O: PIO (physical-log I/O), LIO (logical-log I/O), AIO (asynchronous I/O), and CPU (kernel-asynchronous I/O).
        Network virtual processors
        A client can connect to the database server in the through following ways: a network connection, a pipe, or shared memory.
        Communications support module virtual processor
        The communications support module (CSM) class of virtual processors performs communications support service and communications support module functions.
        Encrypt virtual processors
        Use the VPCLASS configuration parameter with the encrypt keyword to configure encryption VPs.
        Audit virtual processor
        The database server starts one virtual processor in the audit class (ADT) when you turn on audit mode by setting the ADTMODE parameter in the onconfig file to 1.
        Miscellaneous virtual processor
        The miscellaneous virtual processor services requests for system calls that might require a very large stack, such as fetching information about the current user or the host-system name.
        Basic text search virtual processors
        A basic text search virtual processor is required to run basic text search queries.
        MQ messaging virtual processor
        An MQ virtual processor is required to use MQ messaging.
        XML virtual processor
        An XML virtual processor is required to perform XML publishing.
      - Manage virtual processors
        These topics describe how to set the configuration parameters that affect database server virtual processors, and how to start and stop virtual processors.
      - Shared memory
        These topics describe the content of database server shared memory, the factors that determine the sizes of shared-memory areas, and how data moves into and out of shared memory.
      - Manage shared memory
      - Data storage
        The database server uses physical units of storage to allocate disk space. It stores data in logical units. Unlike the logical units of storage whose size fluctuates, each of the physical units has a fixed or assigned size that is determined by the disk architecture.
      - Manage disk space
        You can use several utilities and tools to manage disk spaces and the data that the database server controls.
      - Moving data with external tables
        You can use external tables to load and unload database data.
      - Storage space encryption
        You can encrypt storage spaces (dbspaces, blobspaces and smart blobspaces) with Informix Dynamic Server. The data in encrypted storage spaces is unintelligible without the encryption key. Encrypting storage spaces is an effective way to protect sensitive information that is stored on disk.
    - Logging and log administration
    - Fault tolerance
    - High availability and scalability
      A successful production environment requires database systems that are always available, with minimal if any planned outages, and that can be scaled quickly and easily as business requirements change.
    - Distributed data
    - Overview of automatic monitoring and corrective actions
      You can use the SQL administration API, the Scheduler, and drill-down queries to manage automatic maintenance, monitoring, and administrative tasks.
  - Administrator's Reference
    The Informix® Administrator's Reference includes comprehensive descriptions of HCL Informix configuration parameters, the system-monitoring interface (SMI) tables in the sysmaster database, the syntax of database server utilities such as onmode and onstat, logical-log records, disk structures, event alarms, and unnumbered error messages.
  - DB-Access User's Guide
    The Informix® DB-Access User's Guide describes how to use the DB-Access utility to access, modify, and retrieve information from Informix database servers.
  - High-Performance Loader User's Guide
    The describes how to use the HCL Informix® to load and unload large quantities of data efficiently to or from Informix databases.
  - Performance Guide
    The Informix® Performance Guide describes how to configure and operate your HCL Informix database server to improve overall system throughput and to improve the performance of SQL queries.
  - SNMP Subagent Guide
    The describes the Simple Network Management Protocol (SNMP) and the software that you need to use SNMP to monitor and manage HCL Informix® database servers and databases.
  - InformixHQ Guide
    InformixHQ is a modern web console for visualizing, monitoring, and managing your Informix server instances. It is purpose built for ease-of-use, scaling out, and optimizing DevOps needs. It provides critical performance management capabilities, monitoring how key performance metrics are changing over time and tracking how efficiently Informix is running your workload even when you’ve stepped away from your screen. Its monitoring system feeds directly into a customizable alerting system so you can be immediately alerted via email, Twilio, or PagerDuty whenever an issue occurs on one of your Informix database server instances. InformixHQ is designed to be scalable to efficiently manage and monitor as many Informix database server instances as you need. Moreover, it's a tool that can be shared by the DBAs, the app developers, the ops engineers, and management and accessed from any desktop, laptop, or mobile device. InformixHQ is the centralized hub for graphical monitoring, alerting, and administration of your Informix database servers.
- Backup and Restore Guide
  The Informix® Backup and Restore Guide describes how to use the Informix ON-Bar and ontape utilities to back up and restore database server data. These utilities enable you to recover your databases after data is lost or becomes corrupted due to hardware or software failure or accident.
- Enterprise Replication
  The HCL® Informix® Enterprise Replication Guide describes the concepts of data replication using Informix Enterprise Replication, including how to design your replication system, as well as administer and manage data replication throughout your enterprise.

User-defined virtual processors

User-defined classes of virtual processors protect the database server from ill-behaved user-defined routines.

An ill-behaved user-defined routine has at least one of the following characteristics:

Does not yield control to other threads
Makes blocking operating-system calls
Modifies the global VP state

A well-behaved C-language UDR has none of these characteristics. Run only well-behaved C-language UDRs in a CPU VP.

Warning: Execution of an ill-behaved routine in a CPU VP can cause serious interference with the operation of the database server, possibly causing it to fail or behave erratically. In addition, the routine itself might not produce correct results.

To ensure safe execution, assign any ill-behaved user-defined routines to a user-defined class of virtual processors. User-defined VPs remove the following programming restrictions on the CPU VP class:

The requirement to yield the processor regularly
The requirement to eliminate blocking I/O calls

Functions that run in a user-defined virtual-processor class are not required to yield the processor, and they might issue direct file-system calls that block further processing by the virtual processor until the I/O is complete.

The normal processing of user queries is not affected by ill-behaved traits of a C-language UDR because these UDRs do not execute in CPU virtual processors. For a more detailed explanation of ill-behaved routines, see the Informix® DataBlade® API Programmer's Guide.