Modify PFA cache configuration for pubset
Component: | BS2000 |
Functional area: | Caching media control |
Domain: | MULTI-CATALOG-AND-PUBSET-MGMT |
Privileges: | TSOS |
Function
The MODIFY-PUBSET-CACHE-ATTRIBUTES command enables systems support to define or modify the configuration of a PFA cache, for use as a fast buffer for the data in an SF pubset or in a volume set of an SM pubset.
In addition, the system can be instructed how to behave in the following circumstances:
On pubset startup or cache activation, the desired cache configuration cannot be made available at all or not with the required size (SIZE-TOLERANCE operand).
On pubset startup, the SF pubset or the volume set of an SM pubset can no longer be linked to the cache area assigned in the previous pubset session (FORCE-IMPORT operand).
If the command refers to an SF pubset, there must already be an MRSCAT entry for the pubset. The pubset need not have been imported. The values specified in the command are stored in the pubset’s MRSCAT entry. When the MRSCAT entry is created, the values are assigned default settings.
If the command refers to an SM pubset, there are two different situations to consider:
Modifying the cache configuration of a volume set: The SM pubset to which the volume set belongs must be online. In addition, the status of the volume set must be either “normal use” or “defined only”. The values are stored in the SM pubset’s configuration file. When the SM pubset is generated (or when a volume set is logically added with the MODIFY-PUBSET-DEFINITION-FILE command), the values are initialized with default settings.
Modifying the control information for pubset startup: The SM pubset need not have been imported. The defined values are stored in the pubset’s MRSCAT entry, as they relate to the pubset as a whole and not just to specific volume sets.
The attributes configured with the MODIFY-PUBSET-CACHE-ATTRIBUTES command can be checked with the SHOW-PUBSET-CACHE-ATTRIBUTES command. This information is also contained in the output of the SHOW-PUBSET-PARAMETERS command.
A detailed description of the cache media main memory (*MAIN-MEMORY) will be found in the “DAB” manual [5].
Format
MODIFY-PUBSET-CACHE-ATTRIBUTES | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Operands
PUBSET = <cat-id 1..4>
ID of the pubset for which a cache configuration is to be defined or modified.
PUBSET-TYPE = *SINGLE-FEATURE / *SYSTEM-MANAGED(...)
Specifies the type of pubset for which a new entry is to be created in the MRSCAT.
PUBSET-TYPE = *SINGLE-FEATURE
The pubset is an SF pubset.
PUBSET-TYPE = *SYSTEM-MANAGED(...)
The pubset is an SM pubset. The PFA cache configuration is defined or modified for the volume set specified next.
VOLUME-SET = *UNCHANGED / <cat-id 1..4>
Identifies the volume set.
CACHE-MEDIUM = *UNCHANGED / *NO-CACHE / *MAIN-MEMORY(...)
Identifies the cache medium in which the cache area is to be created. The first prerequisite for this is that the hardware requirements are satisfied, and the second is that a cache handler (DAB), required to serve the cache, is available and is active.
CACHE-MEDIUM = *NO-CACHE
No cache medium is to be used for the specified pubset or volume set. This value is the default in the following cases:
A new MRSCAT entry is created for an SF pubset (ADD-MASTER-CATALOG-ENTRY command).
The initial values are defined for individual volume sets when an SM pubset is generated.
A new volume set entry is generated in the course of dynamic pubset reconfiguration for an SM pubset (MODIFY-PUBSET-DEFINITION-FILE command).
CACHE-MEDIUM = *MAIN-MEMORY(...)
Main memory is to be used as the caching medium.
If there is a system failure, data inconsistencies can arise if the cache medium has also been used as a write cache.
CACHE-SEGMENT-SIZE = *UNCHANGED / *4KB / *8KB / *16KB / *32KB
Governs the size of a cache segment, i.e. the maximum size of the data areas swapped in by DAB in the event of a read miss in the cache. In automated caching (operand CACHED-FILES=*BY-SYSTEM), DAB performs the most favorable prefetch for the file and the current application (regardless of the segment size). In the case of nonautomated caching the following applies: large segments are particularly suitable for sequential processing and for applications with highly localized cache utilization.
Small segments are preferable for applications with a random pattern of access. CACHE-SEGMENT-SIZE=*32 KB is the default in the following cases:
A new MRSCAT entry is created for an SF pubset (ADD-MASTER-CATALOG-ENTRY command).
The initial values are defined for individual volume sets when an SM pubset is generated.
A new volume set entry is generated in the course of dynamic pubset reconfiguration for an SM pubset (MODIFY-PUBSET-DEFINITION-FILE command).
FORCE-OUT = *UNCHANGED / *NO / *AT-LOW-FILLING / *AT-HIGH-FILLING
Defines the intervals at which the contents of the cache are written out to disk.
FORCE-OUT = *NO
The data in the cache is not written out to disk until the file is closed. If no further data can be forced from the cache, subsequent I/O operations can no longer be handled by the cache.
FORCE-OUT = *AT-LOW-FILLING
DAB uses a threshold value to control when the data in the cache is written out to disk. The threshold is when the cache is 25% full. This value is the default in the following cases:
A new MRSCAT entry is created for an SF pubset (ADD-MASTER-CATALOG-ENTRY command).
The initial values are defined for individual volume sets when an SM pubset is generated.
A new volume set entry is generated in the course of dynamic pubset reconfiguration for an SM pubset (MODIFY-PUBSET-DEFINITION-FILE command).
FORCE-OUT = *AT-HIGH-FILLING
DAB uses a threshold value to control when the data in the cache is written out to disk. The threshold is when the cache is 75% full.
CACHED-FILES = *UNCHANGED / *BY-USER-SELECTED / *BY-SYSTEM / *ALL
Governs which files are earmarked for caching.
CACHED-FILES = *BY-USER-SELECTED
The user utilizes performance attributes to specify which files will use the cache. This value is the default in the following cases:
A new MRSCAT entry is created for an SF pubset (ADD-MASTER-CATALOG-ENTRY command).
The initial values are defined for individual volume sets when an SM pubset is generated.
A new volume set entry is generated in the course of dynamic pubset reconfiguration for an SM pubset (MODIFY-PUBSET-DEFINITION-FILE command).
CACHED-FILES = *BY-SYSTEM
The automated, intelligent caching determines which DAB files have an impact on performance. The prefetch factor matching the access profile of the selected files is set and the files are monitored at regular intervals, in order to ensure optimum cache performance.
CACHED-FILES = *ALL
Except for a few system files (file catalog, user catalog, etc.), all the files in the pubset use the cache, which means that files with the performance attribute STD are treated like files with the performance attribute HIGH. The default caching mode is read/write. This form of “blanket caching” should be used only if it can be assumed to have a positive impact on overall performance.
FORCE-IMPORT = *UNCHANGED / *NO / *BY-OPERATOR
Specifies what the system is to do after a system crash, at the next IMPORT-PUBSET, if it is impossible to recreate the link to the cache area which was being used before the crash.
FORCE-IMPORT = *NO
If the link to the cache area is defective, import processing will be terminated. This value is the default setting when a new MRSCAT entry is added with the ADD-MASTER-CATALOG-ENTRY command.
FORCE-IMPORT = *BY-OPERATOR
If the link to the cache area is defective, either import processing will - if allowed by the operator - be continued without accessing the cache storage, or it will be terminated. If it is continued, it should be noted that data inconsistencies can occur in the pubset, and the old cache area will be cleared. Any files which are subject to data inconsistencies are appropriately marked, and can no longer be opened.
CACHE-SIZE = *UNCHANGED / <integer 1..32767>(...)
Indicates the number of storage units to be provided for the cache area in the selected medium.
CACHE-SIZE = <integer 1..32767>(...)
Specifies the number of storage units in kilobytes or megabytes which are to be provided for the cache area in the selected medium. Whether this number is in kilobytes or megabytes is indicated in the substructure below.
DIMENSION = *UNCHANGED / *KILOBYTE / *MEGABYTE
Indicates the dimension of the specified cache size. DIMENSION=*MEGABYTE applies for newly-created entries.
DIMENSION = *KILOBYTE
The value specified for CACHE-SIZE is given in kilobytes. A cache size of less than 32 KB is rounded up to 32 KB. Main memory is the only cache medium which can be sized in KB.
DIMENSION = *MEGABYTE
The value specified for CACHE-SIZE is given in megabytes.
SIZE-TOLERANCE = *UNCHANGED / *YES / *NO
Indicates whether the system is to tolerate a shortage of storage space in the cache when the cache area is created, so that there is less than the amount actually requested by the CACHE-SIZE operand.
SIZE-TOLERANCE = *YES
If the requested size of cache is unavailable (even if there is no cache available), a smaller size should be accepted. This value is the default setting when a new MRSCAT entry is added with the ADD-MASTER-CATALOG-ENTRY command.
SIZE-TOLERANCE = *NO
If the requested size of cache is unavailable, the import processing for this pubset should be terminated.
Return codes
(SC2) | SC1 | Maincode | Meaning |
|---|---|---|---|
0 | CMD0001 | No errors | |
2 | 0 | CMS0002 | Disk error |
1 | CMS0011 | Syntax error | |
1 | CMS0314 | Syntax error for <cat-id> | |
32 | CMD0221 | Internal system error | |
32 | CMS031F | MRS parameter error | |
32 | CMS0310 | Error during privilege checking | |
32 | CMS0317 | MRSCAT is locked | |
32 | CMS0318 | Synchronization error | |
64 | CMS0010 | No authorization for command | |
64 | CMS0312 | MRSCAT entry not found | |
64 | CMS0319 | Pubset type conflict |