GEFILS - switch primary and secondary logical units.

Usage:

mme     gefils

Where:

Q register: must contain zeroes in bits 0-23 and a two-character BCD file code in bits 24-35.

Description:

MME GEFILS switches primary and secondary logical units for a file code. If no secondary unit has been assigned, the peripheral device assigned to the primary logical unit is used.

After a call to MME GEFILS, the A and Q registers will be zero if the file was released or is a system file. Otherwise, the Q register contains the following:

Bits   0-5     Zero
      5-11     Device Address
     12-13     IOM/IOX/IMU/IOP number
     14-15     Reserved for GCOS
     16-23     Eight-bit channel address
     24-35     Reserved for GCOS

and the A register contains the following:

Bits   0-5     Device Code
       6-8     Disposition Code:
                 000  Released
                 001  Dismount
                 010  Save
                 011  Continue
      9-19     Reserved for GCOS
     20-23     High density default from .CROPT
     24-27     Low density default from .CROPT
     28-31     Density from bits 0-3 from PAT word 3
        32     Mode indicator for 1600-bpi tapes
     33-34     Density history bits
        35     Reserved for GCOS

The meaning of tape density values is given in "expl mme gefadd".

When files must be switched, the user program usually must issue mounting/dismounting instructions to the operator; however, with the File and Record Control function, the mounting/dismounting instructions are issued automatically.

The process of purging files is affected by MME GEFILS. If a file has alternate reels which are switched through MME GEFILS (or through a File and Record Control call to FORCE), the reels will not be purged. A multi-reel file using a single tape drive will only have the current reel purged.