Server System Variables The variable value is a list of one or more comma-separated compression algorithm names, in any order, chosen from the following items (not case-sensitive): The default value of  zlib,zstd,uncompressed  indicates that the server permits all compression algorithms. For more information, see Section 4.2.8, “Connection Compression Control” . • zlib : Permit connections that use the  zlib  compression algorithm. • zstd : Permit connections that use the  zstd  compression algorithm (zstd 1.3). • uncompressed : Permit uncompressed connections. If this algorithm name is not included in the  protocol_compression_algorithms  value, the server does not permit uncompressed connections. It permits only compressed connections that use whichever other algorithms are specified in the value, and there is no fallback to uncompressed connections. • protocol_version • proxy_user The version of the client/server protocol used by the MySQL server. If the current client is a proxy for another user, this variable is the proxy user account name. Otherwise, this variable is  NULL . See Section 6.2.18, “Proxy Users” . • pseudo_slave_mode 861 System Variable pseudo_slave_mode Scope Session Dynamic Yes SET_VAR  Hint Applies No System Variable proxy_user Scope Session Dynamic No SET_VAR  Hint Applies No Type String System Variable protocol_version Scope Global Dynamic No SET_VAR  Hint Applies No Type Integer