onmode -p: Add or drop virtual processors

Use the onmode -p command to dynamically add or drop virtual processors for the database server instance. The onmode -p command does not update the onconfig file.

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>>-onmode-- -p--+-+----+--number--+-ADT-----+-+----------------><
                | '- +-'          +-AIO-----+ |   
                |                 +-BTS-----+ |   
                |                 +-CPU-----+ |   
                |                 +-DWAVP---+ |   
                |                 +-ENCRYPT-+ |   
                |                 +-JVP-----+ |   
                |                 +-LIO-----+ |   
                |                 +-MSC-----+ |   
                |                 +-PIO-----+ |   
                |                 +-SOC-----+ |   
                |                 +-STR-----+ |   
                |                 '-vpclass-' |   
                '- - -number--+-BTS-----+-----'   

Element Purpose Key Considerations
-p number Adds or drops virtual processors. The number argument indicates the number of virtual processors to add or drop

If this value is a negative integer, processors are dropped. If this value is a positive integer, processors are added.

You can use the -p option only when the database server is in online mode, and you can add to only one class of virtual processors at a time.

For more details, see Rules for adding and dropping virtual processors.

If you are dropping virtual processors, the maximum cannot exceed the actual number of processors of the specified type. If you are adding virtual processors, the maximum number depends on the operating system.

For more information, see the chapter on using virtual processors in the IBM® Informix Administrator's Guide.

ADT Runs auditing processes The database server starts one virtual processor in the audit class when you turn on audit mode by setting the ADTMODE parameter in the ONCONFIG file.
AIO Performs nonlogging disk I/O to cooked disk spaces Also performs nonlogging I/O to raw disk spaces if kernel asynchronous I/O (KAIO) is not used.
BTS Run basic text search index operations and queries. BTS virtual processors are non-yielding. Specify more BTS virtual processors if you want multiple basic text search queries to be run simultaneously. Use the VPCLASS parameter in the onconfig file to create at least one permanent BTS virtual processor.

For more information on basic text search queries, see the IBM Informix Database Extensions User's Guide.

CPU Runs all session threads and some system threads It is recommended that the number of CPU VPs not be greater than the number of physical processors. If KAIO is used, performs I/O to raw disk spaces, including I/O to physical and logical logs. Runs thread for KAIO where available or a single poll thread. The database server uses the number of CPU VPs to allocate resources for parallel database queries (PDQ). If you drop CPU VPs, your queries will run significantly slower. The Reinit field of the onstat -g mgm output displays information on the number of queries that are waiting for running queries to complete after an onmode -p command. Also see the HCL Informix Performance Guide.
DWAVP Runs the administrative functions and procedures for Informix® Warehouse Accelerator on a database server that is connected to Informix Warehouse Accelerator A single DWAVP can process most Informix Warehouse Accelerator operations without delay. However, in systems with significant activity, you can define a maximum of two DWAVP virtual processors to avoid the delay of other administrative commands while data marts are loading.
ENCRYPT Executes column-level encryption and decryption routines Specify more ENCRYPT virtual processors if you have multiple encrypted columns.
JVP Executes Java™ user-defined routines in the Java Virtual Machine (JVM) Specify more JVPs if you are running many Java UDRs.
LIO Writes to the logical-log files if they are in cooked disk space Use two LIO virtual processors only if the logical logs are in mirrored dbspaces. The database server allows a maximum of two LIO virtual processors.
MSC Manages requests for system calls that require a large stack Used for miscellaneous internal tasks.
PIO Writes to the physical log if it is in cooked disk space Use two PIO virtual processors only if the physical log is in a mirrored dbspace. The database server allows a maximum of two PIO virtual processors.
SOC Uses sockets to perform network communications You can use the SOC virtual processor only if the database server is configured for network connections through sockets.
STR Performs stream pipe connections  
vpclass Names a user-defined virtual processor class Use the VPCLASS parameter in the onconfig to define the user-defined virtual-processor class. Specify more user-defined virtual processors if you are running many UDRs.

On Windows, you can have only one user-defined virtual processor class at a time. Omit the number parameter in the onmode -p vpclass command.

For more information on extension classes, see VPCLASS configuration parameter.

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