6 TS4500 REST API This chapter describes the TS4500 REST API. The TS4500 REST API can be used as an alternative to the TS4500 CLI as a method of  obtaining information from and sending commands to the library.  As of this writing, only the in-band method for sending REST API commands is available.  In-band means that all commands are sent to the library by way of a Control Path drive from  an attached host. Because this process uses SCSI commands, it is called  REST over SCSI (RoS). RoS allows library administrators to obtain status information about library components by  sending REST API (by using SCSI Write Buffer commands) and receiving HTTP responses  (by using Read Buffer commands). If RoS is enabled (the default setting), the library accepts  and responds to commands. If disabled, commands are rejected. For more information about  checking the setting, see 4.3, “Settings” on page 195.  The commands can be sent to the library by using the  sg3_utils  package (Linux) or ITDT. This chapter includes the following topics: 389 ' Copyright IBM Corp. 2014, 2020. All rights reserved. GLYPH<SM590000> 6.4, “HTTP return codes” on page 450 GLYPH<SM590000> 6.3, “Using ITDT for RoS” on page 418 GLYPH<SM590000> 6.2, “Using sg3_utils (Linux)” on page 395 GLYPH<SM590000> 6.1, “REST API Overview” on page 390