Is it permissible to perform the Qiyam prayer if one has not performed the Taraweeh prayer?

It is recommended to perform night prayers (Qiyam al-Layl) both inside and outside of Ramadan. It is more emphasized in Ramadan due to the Prophet's (peace be upon him) saying: "Whoever stands (in night prayer) during Ramadan with faith and expecting Allah's reward, all his past sins will be forgiven." Night prayer is performed by praying between the 'Isha prayer and the emergence of dawn. Performing it in the latter part of the night is better, as stated by Umar (may Allah be pleased with him). Combining prayer at the beginning of the night (Tarawih) and at the end of it (Tahajjud) during the last ten nights is praiseworthy. Performing night prayer in the latter part of the night is not conditional upon having prayed Tarawih, though combining them is better.