Record Management Services (RMS) are procedures in the VMS, RSTS/E, RT-11 and RSX-11M operating systems that programs may call to process files and records within files.^[1][2] Its file formats and procedures are similar to of those in some IBM access methods^[a] for several of its mainframe computer operating systems^[b] and by other vendors for file and record management. VMS RMS is an integral part of the system software; its procedures run in executive mode. (RMS was not initially integrated into RT-11 and RSTS/E, but was available as an added charge "layered product". It was later added to RSTS/E and was a part of its standard documentation set.)

RMS supports four record access methods:

• Sequential Access
• Relative Record Number Access
• Record File Address Access
• Indexed Access

RMS supports four record formats:

• Fixed length
• Variable length
• Variable record length with fixed-length control blocks
• Stream files (records separated by termination characters)
  • STREAM: Records terminated by CRLF
  • STREAM_CR: Records terminated by CR
  • STREAM_LF: Records terminated by LF

Digital provided the File Definition Language (FDL) which could be used to define the structure of an RMS file.^[3]