Introduction › Extending Virtual Database Areas

Extending Virtual Database Areas

CA Datacom strives to provide 24x7 support. When an application needs to add data to a VIRTUAL database area but that area has become full, 24X7 operation is threatened. To minimize that threat, CA Datacom Version 15.0 supports the dynamic extension of VIRTUAL database areas. Previous releases only supported dynamic extension for DASD data sets.

VIRTUAL dynamic extensions are similar to DASD dynamic extensions in the following ways:

• You can define an index area or data area to be subject to dynamic extension so that it activates when more space is required. More space can be required by the addition of an index entry or a data row that cannot fit in the currently defined space.
• You can set an index area or data area to be subject to dynamic extension based upon a console-like command of the chosen size. This form of dynamic extension is called directed dynamic extension. Directed dynamic extension is completely independent of the full file dynamic extension setting.

VIRTUAL dynamic extensions are different from DASD dynamic extensions in the following ways:

• A VIRTUAL area is subject to dynamic extension if a MUF startup option or console-like command defines the area to be subject to dynamic extension. DASD dynamic extensions are based on the selection of a CA Datacom Datadictionary option. VIRTUAL areas accept the CA Datacom Datadictionary information but ignore it for a VIRTUAL base.
• DASD dynamic extensions are subject to Operating System rules regarding making open data sets larger. The basic rules are a maximum of 16 extends per volume and a maximum of 59 volumes. VIRTUAL dynamic extensions are completely within CA Datacom, and CA Datacom supports a maximum single-size extension of between one track and 2 billion bytes. CA Datacom allows you to set the maximum number of dynamic extensions from 0 (none) to 65535 per MUF execution.
• DASD data sets have a secondary allocation value in CYL/TRK/AVGBLK and a number, but VIRTUAL areas do not. The size of extensions for VIRTUAL dynamic extensions must be set in a console-like option or in a directed dynamic extension.
• In prior releases, during a MUF startup, you could define a VIRTUAL database (area) as VIRTUAL dbid-area,size. In Version 15.0, extend-size and extend-count options were added (see extend-size and extend-count in the information about the VIRTUAL startup option).

Using a console-like command, you can change the VIRTUAL dynamic extension options while the MUF is enabled. The command is VIRTUAL_DYNAMIC_EXTEND dbid,area,extend-size,extend-count (see VIRTUAL_DYNAMIC_EXTEND in MUF Startup Options and Console/Console-Like Commands).

64-bit memory is used if allowed and available. If the requirement is not satisfied with 64-bit memory, it is satisfied with Data Space memory, if available.

The MUF EOJ report provides the memory location of 64-bit or Data Space, reports on the placement of the first allocation, and usually represents all parts of the memory. However, if you start with 64-bit at data area open and then extend, Data Space memory is used, and the placement is 64-bit and partly right, but not the full answer.

Dynamic System Table MUF_COVEREDVIRTUAL provides the memory location of 64-bit or Data Space, reports on the placement of the first allocation, and usually represents all parts of the memory. However, if you start with 64-bit at data area open and then extend, Data Space memory is used, and the placement is 64-bit and partly right, but not the full answer (see MUF_COVEREDVIRTUAL (MFC)).

The descriptions of messages DB01705I and DB01706I have been updated to include changes related to VIRTUAL areas. See DB01705I and DB01706I.