The open, close, and end-of-volume (EOV) tape management exits allow tape management systems to avoid changing system control blocks or issuing channel programs against tapes in order to maintain a tape inventory.

During the course of opening, processing and closing a tape data set, the system always calls the File Validation, File Start on volume and File End on Volume. Open or EOV calls the file validation exit for each volume regardless of whether it already was mounted or verified.

Many conditions affect whether various exits are called and their sequence. During one call to Open or EOV, the following is a typical sequence:

1. File end on volume exit (if EOV)
2. Volume mount exit for volume verification (if volume was not previously mounted and verified)
3. Volume mount exit for volume security (if volume was not previously mounted and verified)
4. File validation exit (if labels exist)
5. Volume mount exit for volume write function (if the tape has standard labels, the user is writing and the file is the first file on the volume)
6. File start on volume exit