DCMT VARY Commands › DCMT VARY BUFFER › DCMT VARY BUFFER Usage

DCMT VARY BUFFER Usage

What Happens If CA IDMS Is Actively Using the Buffer

If you issue a VARY BUFFER command for a buffer that is actively in use, the change you request may not occur immediately. You can check the disposition of your request by issuing a DCMT DISPLAY BUFFER command.

Changing Page Count and Storage Characteristics

To implement the following changes, issue the VARY BUFFER command, and close the buffer. When the buffer reopens, the new value(s) is in effect.

• Initial page count
• Additional page count
• Maximum page count
• DC or OPSYS storage

Once you have altered these buffer characteristics, CA IDMS creates a buffer with the new characteristics when you issue a VARY BUFFER command with the OPEN option or when CA IDMS uses the buffer.

Reasons for Changing the Size of the Buffer

Some possible reasons to vary the page count, initial page count, and maximum page count:

• To determine the optimum buffer size based on storage required and the number of buffer I/Os. Once you have determined the optimum values, alter the buffer definitions in the dictionary and regenerate the DMCL.
• To decrease or increase the size of the buffer during non-peak or peak database usage.

Opening a Buffer

Because CA IDMS opens a buffer only when it is needed, you can use the OPEN option to explicitly open the buffer. This option is useful if you are trying to determine the optimum size of the buffer.