| 1 | System pool identifier | Input | Binary(4) |
| 2 | Change request | Input | Char(*) |
| 3 | Length of change request | Input | Binary(4) |
| 4 | Format name | Input | Char(8) |
| 5 | Error code | I/O | Char(*) |
The Change Pool Tuning Information (QWCCHGTN) API changes information about tuning being performed by the system for the different storage pools. The Materialize Resource Management Data (MATRMD) machine interface (MI) instruction can be used to retrieve the current setting of the tuning parameters.
None.
The pool is to be changed. This number corresponds to the number returned on option 9 of the Materialize Resource Management Data (MATRMD) MI instruction. This also corresponds to the identifier shown on the Work with System Status display. This parameter is a value ranging from 2 through 64, where pool 2 is the base pool.
The variable containing the new tuning information. See TUNI0100 Format for the definition of the fields for this parameter.
The length of the change request list. This area must be as large as the format specified.
The format of the information to be changed. The valid values are:
| TUNI0100 | Tuning information for a storage pool. |
The structure in which to return error information. For the format of the structure, see Error code parameter.
The following table shows the information that must be specified in the change request parameter when format TUNI0100 is specified. For a detailed description of each field, see Field Descriptions.
| Offset | Type | Field | |
|---|---|---|---|
| Dec | Hex | ||
| 0 | 0 | CHAR(1) | Type of tuning |
| 1 | 1 | CHAR(1) | Change page handling |
| 2 | 2 | BINARY(4) | Blocking factor for nondatabase objects |
| 6 | 6 | CHAR(1) | Allow exchange operations (for class 1 objects in pool) |
| 7 | 7 | CHAR(1) | Type of transfer from main storage to auxiliary storage (for class 1 objects in pool) |
| 8 | 8 | BINARY(4) | Blocking factor for database (class 1) objects |
| 12 | C | CHAR(1) | Allow exchange operations (for class 2 objects in pool) |
| 13 | D | CHAR(1) | Type of transfer from main storage to auxiliary storage (for class 2 objects in pool) |
| 14 | E | BINARY(4) | Blocking factor for database (class 2) objects |
| 18 | 12 | CHAR(1) | Allow exchange operations (for class 3 objects in pool) |
| 19 | 13 | CHAR(1) | Type of transfer from main storage to auxiliary storage (for class 3 objects in pool) |
| 20 | 14 | BINARY(4) | Blocking factor for database (class 3) objects |
| 24 | 18 | CHAR(1) | Allow exchange operations (for class 4 objects in pool) |
| 25 | 19 | CHAR(1) | Type of transfer from main storage (for class 4 objects in pool) to auxiliary storage |
| 26 | 1A | BINARY(4) | Blocking factor for database (class 4) objects |
When tuning is requested (values 1, 2, or 3 for the type of tuning field), the system periodically categorizes database objects into four different performance classes. The classes are:
| Class 1 | Object access appears to be random. A disk access is required for nearly each record that is accessed. |
| Class 2 | Locality of reference detected. Several records are being accessed per disk access. |
| Class 3 | High locality of reference detected. The object is being processed in a sequential manner; references are highly clustered and large portions of the object are resident in main storage. |
| Class 4 | The class of a database object is adjusted if the object's size is small in comparison to the available storage in the storage pool. This class adjustment involves adding 1 to the class number; therefore, a class 3 database object (as defined above) would be treated as a class 4 if it were small in comparison to the available storage in the storage pool. |
Reference information for determining an object's class is collected periodically. It is collected by storage pool because an object's class varies over time and by storage pool.
Note: When a new system pool is created as a result of starting a subsystem, the type of tuning and change page handling attributes for the new system pool are initialized based on the type of storage pool being created. For shared storage pools, the type of tuning and change page handling attributes are set based on the paging option defined for the shared storage pool. For private storage pools, the type of tuning attribute is set to indicate no tuning should be done and the change page handling attribute is set to the system default value.
Allow exchange operations. The exchange operation used to reduce the working set size. This is done by overlaying data that is already in main storage with new data this is being brought into main storage. The values for this field are:
| 0 | Use the system default, which is 1 (allow exchange operations) |
| 1 | Allow exchange operations |
| 2 | Disable exchange operations |
| 3 | Disable exchange operations (The data that already exists in main storage should be a good candidate to be replaced when additional storage is needed in the storage pool.) |
The value specified for this field is ignored unless static tuning is specified for the type of tuning field.
Blocking factor for database objects. The amount of data that should be brought into main storage when a request is made to read database objects from auxiliary storage. The values for this field are:
| 0 | Use the system default, which is 4 (transfer data into main storage in 4KB blocks) |
| 4 | Transfer data into main storage in 4KB blocks |
| 8 | Transfer data into main storage in 8KB blocks |
| 16 | Transfer data into main storage in 16KB blocks |
| 32 | Transfer data into main storage in 32KB blocks |
| 64 | Transfer data into main storage in 64KB blocks |
| 128 | Transfer data into main storage in 128KB blocks |
The system may need to issue multiple I/O operations to bring the data into main storage. The value specified for the blocking factor for database objects field is ignored unless static tuning is specified for the type of tuning field.
Blocking factor for nondatabase objects. The amount of data that should be brought into main storage when a request is made to read nondatabase objects from auxiliary storage. The possible values for this field are:
| 0 | Use the system default, which is 4 (transfer data into main storage in 4KB blocks) |
| 4 | Transfer data into main storage in 4KB blocks |
| 8 | Transfer data into main storage in 8KB blocks |
| 16 | Transfer data into main storage in 16KB blocks |
| 32 | Transfer data into main storage in 32KB blocks |
The system may need to issue multiple I/O operations to bring the data into main storage. The value specified for the blocking factor for nondatabase objects is ignored unless static tuning is specified for the type of tuning field.
Change page handling. The method the system uses to determine when to write changed pages to auxiliary storage. The values for this field are:
| 0 | Use the system default, which is 1 (Changed pages should be written to auxiliary storage when there is a demand for pages in a storage pool.) |
| 1 | Changed pages should be written to auxiliary storage when there is a demand for pages in a storage pool |
| 2 | In addition to writing changed pages on demand, periodically write changed pages to auxiliary storage |
Type of transfer from main storage to auxiliary storage. The method the system uses to process a request to write an object to auxiliary storage. The values for this field are:
| 0 | Use the system default, which is 1 (When objects are changed, write the changes to auxiliary storage. Indicate that the portion of the object that was written to auxiliary storage should be a good candidate to be replaced when additional storage is needed in the storage pool.) |
| 1 | When objects are changed, write the changes to auxiliary storage. Indicate that the portion of the object that was written to auxiliary storage should be a good candidate to be replaced when additional storage is needed in the storage pool. |
| 2 | When objects are changed, write the changes to auxiliary storage. |
| 3 | Do not immediately write the changes to auxiliary storage. Indicate that the portion of the object that was changed should be a good candidate to be replaced when additional storage is needed in the storage pool. |
| 4 | Do not immediately write the changes to auxiliary storage. |
The value specified for this field is ignored unless static tuning is specified for the type of tuning field.
Type of tuning. The method used by the system to tune the storage pool. The values for this field are:
| 0 | No tuning is being performed for this pool.
All values specified for the blocking factor, the allow exchange operations, and the type of transfer from main storage to auxiliary storage fields are ignored. The system default values are used for all these fields. |
| 1 | Static tuning is being performed for this pool.
Static tuning implies that the values specified for blocking factor, exchange
operation, and transfers to auxiliary storage are not dynamically adjusted by
the system.
Values must be specified for the blocking factor, allow exchange operations, and type of transfer from main storage to auxiliary storage for the storage pools. |
| 2 | Dynamic tuning of transfers into main storage is
being performed. This indicates that the system is dynamically adjusting the
blocking factor and exchange operations.
Because the values for blocking factor and allow exchange operations are dynamically adjusted, the values specified on the API are ignored. The value used for the transfer to auxiliary storage field is set to ensure that requests to write data to auxiliary storage are processed immediately. |
| 3 | Dynamic tuning of transfers into main storage and
to auxiliary storage is being performed. This indicates that the system is
dynamically adjusting the blocking factor, exchange operations, and transfers
to auxiliary storage.
Because the values for the blocking factor, allow exchange operations, and transfers to auxiliary storage are dynamically adjusted, the values specified on the API are ignored. |
| Message ID | Error Message Text |
|---|---|
| CPF1001 E | Wait time expired for system response. |
| CPF1870 E | Value &1 for type of tuning not valid. |
| CPF1871 E | Value &1 for change page handling not valid. |
| CPF1872 E | Value &1 for blocking factor not valid. |
| CPF1873 E | Value &1 for exchange operation not valid. |
| CPF1874 E | Value &1 for transfer to auxiliary storage not valid. |
| CPF1875 E | Value &1 for change request length not valid. |
| CPF1876 E | Value &1 for pool number not valid. |
| CPF24B4 E | Severe error while addressing parameter list. |
| CPF3CF1 E | Error code parameter not valid. |
| CPF3CF2 E | Error(s) occurred during running of &1 API. |
| CPF3C21 E | Format name &1 is not valid. |
| CPF3C90 E | Literal value cannot be changed. |
| CPF9872 E | Program or service program &1 in library &2 ended. Reason code &3. |