It is possible for systems support to use the parameter service to determine which volumes are to be used for paging. Care is required here to ensure that paging files with the name SYS.PAGING.<vsn> have been created on these volumes and that the maximum permissible number of paging files cannot be used at startup (see below).
The paging area initialized at startup must be at least 50 Mbytes in size, otherwise system initialization will be aborted with message NSI5225. If the paging area is larger than 50 Mbytes but smaller than 200 Mbytes, a warning in the form of message NSI5115 is output on the console, but system initialization continues.
By selecting appropriate paging files to be used for paging, it is possible, as early as startup, to direct paging activity to less heavily utilized volumes.
Not all the paging volumes specified for paging need to be available and usable at startup time since additional paging files can be brought into use during a session.
If systems support did not specify any parameters for paging file selection, all the SYS.PAGING.<vsn> files created on the home pubset are automatically used for paging.
The parameter service allows volumes with paging files both from the home pubset and from other pubsets to be specified.
Restrictions
At startup time at least one paging disk must be specified or (with no parameters specified) at least one paging file must be set up on the home pubset.
A maximum of 128 paging disks may be specified at startup time.
Each paging file
SYS.PAGING.<vsn>can consist of a number of extents, but all of these must be on the same disk. However, additional extents reduce the maximum number of usable paging files: For example, if each file has 2 extents, the startup table only accommodates 102 rather than 128 paging files; if there are 64 files, these may have a maximum of 320 extents.The paging files specified at startup may be distributed over a maximum of 16 pubsets.
If a paging file cannot be found for a specified disk, this disk is ignored (message
NSI5110 ).Private disks cannot be used for paging.
Paging pubsets must be available in their entirety and exclusively; i.e. they must not be shared pubsets. They are reserved in their entirety and exclusively for the forthcoming session by startup paging initialization. In the case of an SM pubset, only the volume set which contains the paging disks is checked for external allocations.
The system initialization device configuration stored in IPL.CONF is automatically extended by any newly specified paging disks.
The keyword for the BEGIN record is PAGING.
The maximum number of parameter records allowed for this is 16. Any further specifications are ignored (message NSI0049) and system initialization continues. If a syntax error is diagnosed in the PAGING statement during system initialization, this statement is rejected without specification of a reason.
On the console, the statement can either be repeated with the correct values or ignored.
Format of the parameter record for selecting the paging areas at startup time
Instruction | Operand |
PAGING | VOLUME = vsn / (vsn,...,vsn) |
VOLUME =
Volumes to be used for paging. The volume serial number VSN is always 6 characters in length.
The following rules apply:
Two or more identical volume specifications are interpreted as a single entry.
A maximum of 128 VSN specifications can be processed (16 parameter records with a maximum of 8 VSNs each). Any further specifications are ignored (message
NSI0049) and system initialization continues.If all specified paging statements are ignored due to syntax errors, all paging files
SYS.PAGING.<vsn>set up on the home pubset are automatically used for paging.In a BS2000 session, it is always possible to use combinations of different types of disk simultaneously for paging (with respect to performance, see also the “Performance Handbook” [37]).
Extract from the parameter file
/BS2000 PARAMS : /BEGIN PAGING PAGING VOLUME=(PUBA01,PUBA02,PUBB01,PUBB02,PUBB03) 1. PAGING VOLUME=ABC.01 2. /EOF : /END-PARAMS
The paging files (
SYS.PAGING.<vsn>) on the specified volumes of the pubsets with the catalog IDs A and B become part of the paging area at startup.The paging file on the specified volume of the pubset with the catalog ID ABC is to be counted as part of the paging area at startup.