The details of the configuration items allowed in databases.conf are documented in chapter Chapter 3, firebird.conf.
The following configurations items are supported:
Section 3.1.2, “RemoteAccess”
Section 3.1.3, “ExternalFileAccess”
Section 3.1.6, “TempTableDirectory”
Section 3.1.9, “DefaultDbCachePages”
Section 3.1.10, “DatabaseGrowthIncrement”
Section 3.1.11, “UseFileSystemCache”
Section 3.1.16, “TempCacheLimit”
Section 3.1.17, “MaxIdentifierByteLength”
Section 3.1.18, “MaxIdentifierCharLength”
Section 3.1.19, “InlineSortThreshold”
Section 3.1.20, “OptimizeForFirstRows”
Section 3.1.21, “OuterJoinConversion”
Section 3.1.22, “SubQueryConversion”
Section 3.1.23, “AuthServer”
Section 3.1.24, “AuthClient”
Section 3.1.25, “UserManager”
Section 3.1.26, “DefaultProfilerPlugin”
Section 3.1.28, “WireCryptPlugin”
Section 3.1.29, “KeyHolderPlugin”
Section 3.1.31, “Providers”
Section 3.1.32, “DeadlockTimeout”
Section 3.1.33, “StatementTimeout”
Section 3.1.34, “ConnectionIdleTimeout”
Section 3.1.35, “OnDisconnectTriggerTimeout”
Section 3.1.36, “MaxUnflushedWrites”
Section 3.1.37, “MaxUnflushedWriteTime”
Section 3.1.39, “ClearGTTAtRetaining”
Section 3.1.42, “DataTypeCompatibility”
Section 3.1.44, “WireCrypt”
Section 3.1.46, “DummyPacketInterval”
Section 3.1.51, “RemoteAuxPort”
Section 3.1.57, “LockMemSize”
Section 3.1.58, “LockAcquireSpins”
Section 3.1.59, “LockHashSlots”
Section 3.1.60, “EventMemSize”
Section 3.1.61, “SnapshotsMemSize”
Section 3.1.62, “TipCacheBlockSize”
Section 3.1.65, “GCPolicy”
Section 3.1.66, “MaxStatementCacheSize”
Section 3.1.67, “SecurityDatabase”