Use of prestart jobs

A prestart job is a batch job that starts running before a program on a remote system initiates communications with the server.

Prestart jobs use prestart job entries in the subsystem description to determine which program, class, and storage pool to use when the jobs are started. Within a prestart job entry, you must specify attributes for the subsystem to use to create and to manage a pool of prestart jobs.

Prestart jobs increase performance when you initiate a connection to a server. Prestart job entries are defined within a subsystem. Prestart jobs become active when that subsystem is started, or they can be controlled with the Start Prestart Job (STRPJ) and End Prestart Job (ENDPJ) commands.

System information that pertains to prestart jobs (such as DSPACTPJ) uses the term 'program start request' exclusively to indicate requests made to start prestart jobs, even though the information may pertain to a prestart job that was started as a result of a sockets connection request.

Notes:

Prestart jobs can be reused, but there is no automatic cleanup for the prestart job once it has been used and subsequently returned to the pool. The number of times the prestart job is reused is determined by the value specified for the maximum number of uses (MAXUSE) value of the ADDPJE or CHGPJE CL commands. This means that resources that are used by one user of the prestart job must be cleaned up before ending use of the prestart job. Otherwise, these resources will maintain the same status for the next user that uses the prestart job. For example, a file that is opened but never closed by one user of a prestart job remains open and available to the following user of the same prestart job.
By default, some of the server jobs run in QUSRWRK or QSERVER. Using iSeries™ Navigator, you can configure some or all of these servers to run in a subsystem of your choice.
1. Double-click iSeries Navigator > Network > Servers > iSeries Access.
2. Right-click the server that you want to configure subsystems for and select Properties.
3. Configure the server using the Subsystems page.
If you move jobs from the default subsystem, you must:
1. Create your own subsystem description.
2. Add your own prestart job entries using the ADDPJE command. Set the STRJOBS parameter to *YES.
If you do not do this, your jobs will run in the default subsystem.

All of the host servers that are supported by the sockets communications interface support prestart jobs.

These servers are:

Network print server
Remote command and distributed program call server
Central server
Database server
Secure database server
File server
Secure file server
Data queue server
Signon server (unique to servers using sockets communications support)

The following lists provide each of the prestart job entry attributes, and provide the initial values that are configured for the host servers using sockets communications support.

Subsystem description

The subsystem that contains the prestart job entries.

Host server	Value
Network Print	QUSRWRK
Remote command and program call	QUSRWRK
Central	QUSRWRK
Database	QUSRWRK
Secure Database	QUSRWRK
File	QSERVER
Secure File	QSERVER
Data Queue	QUSRWRK
Signon	QUSRWRK

Program library/name

The program that is called when the prestart job is started.

Host server	Value
Network Print	QSYS/QNPSERVS
Remote command and program call	QSYS/QZRCSRVS
Central	QSYS/QZSCSRVS
Database	QSYS/QZDASOINIT
Secure Database	QSYS/QZDASSINIT
File	QSYS/QPWFSERVSO
Secure File	QSYS/QPWFSERVSS
Data Queue	QSYS/QZHQSSRV
Signon	QSYS/QZSOSIGN

User profile

The user profile that the job runs under. This is what the job shows as the user profile. When a request to start a server is received from a client, the prestart job function switches to the user profile that is received in that request.

Host server	Value
Network Print	QUSER
Remote command and program call	QUSER
Central	QUSER
Database	QUSER
Secure Database	QUSER
File	QUSER
Secure File	QUSER
Data Queue	QUSER
Signon	QUSER

Job name

The name of the job when it is started.

Host server	Value
Network Print	*PGM
Remote command and program call	*PGM
Central	*PGM
Database	*PGM
Secure Database	*PGM
File	*PGM
Secure File	*PGM
Data Queue	*PGM
Signon	*PGM

Job description

The job description used for the prestart job. Note that if *USRPRF is specified, the job description for the profile that this job runs under will be used. This means QUSER's job description will be used. Some attributes from the requesting user's job description are also used; for example, print device and output queue are swapped from the requesting user's job description.

Host server	Value
Network Print	QSYS/QZBSJOBD
Remote command and program call	QSYS/QZBSJOBD
Central	QSYS/QZBSJOBD
Database	QGPL/QDFTSVR
Secure Database	QGPL/QDFTSVR
File	QGPL/QDFTSVR
Secure File	QGPL/QDFTSVR
Data Queue	QSYS/QZBSJOBD
Signon	QSYS/QZBSJOBD

Start jobs

Indicates whether prestart jobs are to automatically start when the subsystem is started. These prestart job entries are shipped with a start jobs value of *YES to ensure that the server jobs are available. The STRHOSTSVR command starts each prestart job as part of its processing.

Host server	Value
Network Print	*YES
Remote command and program call	*YES
Central	*YES
Database	*YES
Secure Database	*YES
File	*YES
Secure File	*YES
Data Queue	*YES
Signon	*YES

Initial number of jobs

The number of jobs that are started when the subsystem starts. This value is adjustable to suit your particular environment and needs.

Host server	Value
Network Print	1
Remote command and program call	1
Central	1
Database	1
Secure Database	1
File	1
Secure File	1
Data Queue	1
Signon	1

Threshold

The minimum number of available prestart jobs for a prestart job entry. When this threshold is reached, additional prestart jobs automatically start. Threshold maintains a certain number of jobs in the pool.

Host server	Value
Network Print	1
Remote command and program call	1
Central	1
Database	1
Secure Database	1
File	1
Secure File	1
Data Queue	1
Signon	1

Additional number of jobs

The number of additional prestart jobs that are started when the threshold is reached.

Host server	Value
Network Print	2
Remote command and program call	2
Central	2
Database	2
Secure Database	2
File	2
Secure File	2
Data Queue	2
Signon	2

Maximum number of jobs

The maximum number of prestart jobs that can be active for this entry.

Host server	Value
Network Print	*NOMAX
Remote command and program call	*NOMAX
Central	*NOMAX
Database	*NOMAX
Secure Database	*NOMAX
File	*NOMAX
Secure File	*NOMAX
Data Queue	*NOMAX
Signon	*NOMAX

Maximum number of uses

The maximum number of uses of the job. A value of 200 indicates that the prestart job will end after 200 requests to start the server have been processed.

Host server	Value
Network Print	200
Remote command and program call	1
Central	200
Database	200
Secure Database	200
File	*NOMAX
Secure File	*NOMAX
Data Queue	200
Signon	200

Wait for job

This causes a client connection request to wait for an available server job if the maximum number of jobs has been reached.

Host server	Value
Network Print	*YES
Remote command and program call	*YES
Central	*YES
Database	*YES
Secure Database	*YES
File	*YES
Secure File	*YES
Data Queue	*YES
Signon	*YES

Pool identifier

The subsystem pool identifier in which this prestart job runs.

Host server	Value
Network print	1
Remote command and program call	1
Central	1
Database	1
Secure database	1
File	1
Secure file	1
Data queue	1
Signon	1

Class

The name and library of the class the prestart job runs under.

Host server	Value
Network Print	QGPL/QCASERVR
Remote command and program call	QGPL/QCASERVR
Central	QGPL/QCASERVR
Database	QSYS/QPWFSERVER
Secure Database	QSYS/QPWFSERVER
File	QSYS/QPWFSERVER
Secure File	QSYS/QPWFSERVER
Data Queue	QGPL/QCASERVR
Signon	QGPL/QCASERVR

When the start jobs value for the prestart job entry has been set to *YES and the remaining values are at their initial settings, the following actions take place for each prestart job entry:

When the subsystem is started, one prestart job for each server is started.
When the first client connection request processes for a specific server, the initial job is used and the threshold is exceeded.
Additional jobs are started for that server based on the number that is defined in the prestart job entry.
The number of available jobs is always at least one.
The subsystem periodically checks the number of prestart jobs that are ready to process requests, and ends excess jobs. The subsystem always leaves at least the number of prestart jobs specified in the initial jobs parameter.

Monitor prestart jobs

Use the Display Active Prestart Jobs (DSPACTPJ) command to monitor the prestart jobs. For example, to monitor prestart jobs for the signon server, you must know the subsystem your prestart jobs are in (QUSRWRK or a user-defined subsystem) and the program (for example, QZSOSIGN).

The DSPACTPJ command provides the following information:

+--------------------------------------------------------------------------------+
|                   Display Active Prestart Jobs                 AS400597        |
|                                                      01/12/95  16:39:25        |
|Subsystem  . . . . . :   QUSRWRK       Reset date . . . . . :   01/11/95        |
|Program  . . . . . . :   QZSOSIGN      Reset time . . . . . :   16:54:50        |
|  Library  . . . . . :     QSYS      Elapsed time . . . . :   0023:12:21        |
|                                                                                |
| Prestart jobs:                                                                 |
|   Current number . . . . . . . . . . . . . . . . :   10                        |
|   Average number . . . . . . . . . . . . . . . . :   8.5                       |
|   Peak number  . . . . . . . . . . . . . . . . . :   25                        |
|                                                                                |
| Prestart jobs in use:                                                          |
|   Current number . . . . . . . . . . . . . . . . :   5                         |
|   Average number . . . . . . . . . . . . . . . . :   4.3                       |
|   Peak number  . . . . . . . . . . . . . . . . . :   25                        |
|                                                                                |
|                                                                                |
|                                                             More...            |
|                                                                                |
|                                                                                |
+--------------------------------------------------------------------------------+

+--------------------------------------------------------------------------------+
|                                                      01/12/95  16:39:25        |
|Subsystem  . . . . . :   QUSRWRK       Reset date . . . . . :   01/11/95        |
|Program  . . . . . . :   QZSOSIGN      Reset time . . . . . :   16:54:50        |
|  Library  . . . . . :     QSYS      Elapsed time . . . . :   0023:12:21        |
|                                                                                |
|                                                                                |
|                                                                                |
| Program start requests:                                                        |
|   Current number waiting . . . . . . . . . . . . :   0                         |
|   Average number waiting . . . . . . . . . . . . :   .2                        |
|   Peak number waiting  . . . . . . . . . . . . . :   4                         |
|   Average wait time  . . . . . . . . . . . . . . :   00:00:20.0                |
|   Number accepted  . . . . . . . . . . . . . . . :   0                         |
|   Number rejected  . . . . . . . . . . . . . . . :   0                         |
|                                                                                |
|                                                                                |
|                                                                                |
|                                                             Bottom             |
|Press Enter to continue.                                                        |
|                                                                                |
|F3=Exit   F5=Refresh   F12=Cancel   F13=Reset statistics                        |
|                                                                                |
+--------------------------------------------------------------------------------+

Manage prestart jobs

Pressing the F5 key while on the Display Active Prestart Jobs display can refresh the information presented for an active prestart job. The information about program start requests can indicate whether you need to change the available number of prestart jobs. If the information indicates that program start requests are waiting for an available prestart job, you can change prestart jobs with the Change Prestart Job Entry (CHGPJE) command.

If the program start requests are not acted on quickly, you can do any combination of the following:

Increase the threshold
Increase the parameter value for the initial number of jobs (INLJOBS)
Increase the parameter value for the additional number of jobs (ADLJOBS)

The key is to ensure that an available prestart job exists for every request.

Remove prestart job entries

If you decide that you do not want the servers to use the prestart job function, you must do the following:

End the prestarted jobs with the End Prestart Job (ENDPJ) command.
Prestarted jobs ended with the ENDPJ command are started the next time the subsystem is started if start jobs *YES is specified in the prestart job entry or when the STRHOSTSVR command is issued for the specified server type. If you only end the prestart job and don't take the next step, any requests to start the particular server will fail.
Remove the prestart job entries in the subsystem description with the Remove Prestart Job Entry (RMVPJE) command.
The prestart job entries that are removed with the RMVPJE command are permanently removed from the subsystem description. Once the entry is removed, new requests for the server will succeed.

Use routing entries

When a daemon job is routed to a subsystem, the job is using the routing entries in the subsystem description. The routing entries for the host server daemon jobs are added to the subsystem description when the STRHOSTSVR command is issued. These jobs are started under the QUSER user profile. For daemon jobs that are submitted to the QSYSWRK subsystem, the QSYSNOMAX job queue is used. For daemon jobs that are submitted to the QSERVER subsystem, the QPWFSERVER job queue is used.

The characteristics of the server jobs are taken from their prestart job entry. If prestart jobs are not used for the servers, then the server jobs start with the characteristics of their corresponding daemon jobs.

The following information provides the initial configuration in the IBM-supplied subsystems for each of the server daemon jobs.

Network print server daemon

Subsystem	QSYS/QSYSWRK
Job queue	QSYSNOMAX
User	QUSER
Route data	QNPSERVD
Job name	QNPSERVD
Class	QGPL/QCASERVR
Sequence number	2538

Remote command and program call server daemon

Subsystem	QSYS/QSYSWRK
Job queue	QSYSNOMAX
User	QUSER
Route data	QZRCSRVSD
Job name	QZRCSRVSD
Class	QGPL/QCASERVR
Sequence number	2539

Central server daemon

Subsystem	QSYS/QSYSWRK
Job queue	QSYSNOMAX
User	QUSER
Route data	QZSCSRVSD
Job name	QZSCSRVSD
Class	QGPL/QCASERVR
Sequence number	2536

Database server daemon

Subsystem	QSYS/QSERVER
Job queue	QPWFSERVER
User	QUSER
Route data	QZDASRVSD
Job name	QZDASRVSD
Class	QSYS/QPWFSERVER
Sequence number	600

File server daemon

Subsystem	QSYS/QSERVER
Job queue	QPWFSERVER
User	QUSER
Route data	QPWFSERVSD
Job name	QPWFSERVSD
Class	QSYS/QPWFSERVER
Sequence number	200

Data queue server daemon

Subsystem	QSYS/QSYSWRK
Job queue	QSYSNOMAX
User	QUSER
Route data	QZHQSRVD
Job name	QZHQSRVD
Class	QGPL/QCASERVR
Sequence number	2537

Signon server daemon

Subsystem	QSYS/QSYSWRK
Job queue	QSYSNOMAX
User	QUSER
Route data	QZSOSGND
Job name	QZSOSGND
Class	QGPL/QCASERVR
Sequence number	2540

Server Mapper daemon

Subsystem	QSYS/QSYSWRK
Job queue	QSYSNOMAX
User	QUSER
Route data	QZSOSMAPD
Job name	QZSOSMAPD
Class	QGPL/QCASERVR
Sequence number	2541