Physical Database DDL Statements › BUFFER Statements › Entity Currency › Usage

Usage

Buffer Storage Not Acquired Until Needed

CA IDMS/DB does not acquire storage for a buffer until it opens a file associated with the buffer.

Buffer Page Count Under the Central Version

When you start up a DC/UCF system, the number of pages in a given buffer is the number specified in the INITIAL PAGES parameter in the buffer definition. If the initial number of pages is lower than the number specified in the MAXIMUM PAGES parameter, you can use the DCMT VARY BUFFER command to increase the number of pages in the buffer up to the specified maximum.

How CA IDMS/DB Acquires Storage for a Buffer

The OPSYS and IDMS parameters tell CA IDMS/DB how to acquire storage for the buffer. In response to the OPSYS parameter, CA IDMS/DB issues a request to the operating system for a contiguous block of storage for the buffer pages. In response to the IDMS parameter, CA IDMS/DB issues requests to the DC/UCF system for storage equal to the size of a buffer page until all the required pages are acquired. For both OPSYS and IDMS, CA IDMS/DB acquires the storage above the 16-megabyte line, if possible.

Dropping a Buffer with Associated Files

Before you delete the definition of a buffer, use the ALTER DMCL statement to change the buffer specification for files associated with the buffer.