On operating systems that support large files, Synergy DBL supports individual ISAM files (.ism and .is1) of up to 256 terabytes in size. To create a terabyte file, specify the TBYTE option in the ISAMC subroutine. By default, ISAM files are limited to 2 GB.
On Windows, terabyte files are supported by Synergy and xfServer/xfServerPlus only on systems with the NTFS file system. They are not supported on FAT or FAT32 file systems.
On Unix, some operating systems require you to set a large-file option on the file system being used. Some (AIX in particular) require this to be done when the file system is first created, and others allow the option to be added later.
When creating an ISAM file, you can declare a minimum record size of 4 bytes (5 for TBYTE files) and a maximum of 65,535 bytes minus the following overhead:
- Each duplicate key adds 3 bytes (4 bytes if TBYTE).
- All file types except fixed-length without compression add 2 bytes.
- Variable adds 2 bytes.
- Stored GRFA adds 4 bytes.
- Static RFAs on any file type except fixed-length adds 6 bytes.
- One delete byte is automatically added.
- Change tracking adds 12 bytes.
On OpenVMS, the maximum RMS record size is 32,234.
